Patternable low-k dielectric interconnect structure with a graded cap layer and method of fabrication

ABSTRACT

An interconnect structure is provided that includes at least one patterned and cured low-k material located on a surface of a patterned graded cap layer. The at least one cured and patterned low-k material and the patterned graded cap layer each have conductively filled regions embedded therein. The patterned and cured low-k material is a cured product of a functionalized polymer, copolymer, or a blend including at least two of any combination of polymers and/or copolymers having one or more acid-sensitive imageable groups, and the graded cap layer includes a lower region that functions as a barrier region and an upper region that has antireflective properties of a permanent antireflective coating.

FIELD OF THE INVENTION

The present disclosure generally relates to interconnect structures andmethods of fabricating the same. Specifically, the present disclosureprovides single-damascene and dual-damascene low-k interconnectstructures each including at least one cured product of a patternablelow-k dielectric located on a graded cap layer and methods offabricating the same.

BACKGROUND OF THE INVENTION

It is widely known that the speed of propagation of interconnect signalsis one of the most important factors controlling overall circuit speedas feature sizes are reduced and the number of devices per unit area aswell as the number of interconnect levels are increased. Throughout thesemiconductor industry, there has been a strong drive to increase theaspect ratio (i.e., height to width ratio) and to reduce the dielectricconstant, k, of interlayer dielectric (ILD) materials used toelectrically insulate metal conductive lines. As a result, interconnectsignals travel faster through conductors due to a reduction inresistance-capacitance (RC) delays.

State-of-the-art semiconductor chips employ copper (Cu) as theelectrical conductor and inorganic organosilicates as the low dielectricconstant (low-k) dielectric, and have up to twelve levels of Cu/low-kinterconnect layers. These Cu/low-k interconnect layers are fabricatedwith an iterative additive process, called dual-damascene, whichincludes several processing steps, which are described in greater detailin the following paragraphs.

When fabricating integrated circuit wiring within a multi-layeredscheme, an insulating or dielectric material, e.g., silicon oxide or alow-k insulator will normally be patterned with several thousandopenings to create conductive line openings and/or via openings usingphoto patterning and plasma etching techniques, e.g., photolithographywith subsequent etching by plasma processes.

Unfortunately, the strategy to introduce low-k materials (typicallydielectrics whose dielectric constant is below that of silicon oxide)into advanced interconnects is difficult to implement due to the newmaterials chemistry of the low-k materials that are being introduced.Moreover, low-k dielectrics exhibit fundamentally weaker electrical andmechanical properties as compared to silicon oxide. Moreover, the low-kdielectric alternatives are typically susceptible to damage during thevarious interconnect processing steps. The damage observed in the low-kdielectric materials is manifested by an increase in the dielectricconstant and increased moisture uptake, which may result in reducedperformance and device reliability.

One way to overcome the integration challenges of low-k materials is toprotect these low-k dielectric materials by adding at least onesacrificial hardmask layer onto a surface of the low-k dielectricmaterial. While the hardmask layer serves to protect the low-k material,the presence of the sacrificial hardmask layer adds enormous processcomplexity as more film deposition, pattern transfer etch, and removalof hardmask layers are needed.

A state-of-the-art back-end-of-the-line (BEOL) integration process,called a low temperature oxide (LTO) process, employs up to eight layersof sacrificial hardmask materials to fabricate a two-layerdual-damascene interconnect structure. For example, a via-first LTOintegration for forming a dual-damascene interconnect includes the stepsof: depositing a dielectric material on a substrate including apatterned conductor; forming at least one via in the dielectricmaterial, such that at least one of the vias is positioned over thepatterned conductor; depositing a layer of planarizing material on thedielectric material and in the via; depositing a layer of barriermaterial on the layer of planarizing material; depositing at least onelayer of imaging material on the layer of barrier material; forming atleast one trench in the imaging material, barrier material andplanarizing material, such that the at least one trench is positionedover the via; removing the imaging material, either after orconcurrently with forming the trench in the planarizing material;transferring the at least one trench to the dielectric material, suchthat at least one of the trenches is positioned over the via; removingthe barrier material, either after or concurrently with transferring theat least one trench to the dielectric material; and removing theplanarizing material.

A line-first LTO integration for forming a dual-damascene interconnectstructure includes the steps of: depositing a dielectric material on asubstrate including a patterned conductor; forming at least one trenchin the dielectric material, such that the at least one trench ispositioned over the patterned conductor; depositing a layer ofplanarizing material on the dielectric material and in the trench;depositing a layer of barrier material on the layer of planarizingmaterial; depositing at least one layer of imaging material on the layerof barrier material; forming at least one via in the imaging material,barrier material and planarizing material, such that at least one of thevias is positioned over the trench and the patterned conductor; removingthe imaging material, either after or concurrently with forming the viain the planarizing material; transferring the at least one via to thedielectric material, such that at least one of the vias is positionedover the trench and the patterned conductor; removing the barriermaterial, either after or concurrently with transferring the at leastone via to the dielectric material; and removing the planarizingmaterial.

The integration schemes, such as the LTO one mentioned above, are verycomplex, inefficient, and costly. For example, the via-first LTOintegration scheme requires ten layers of films and twenty-one processsteps to form a two-layer dual-damascene dielectric structure. In otherwords, 80% of films are not needed in the final interconnect structure.

Although immensely popular in semiconductor manufacturing, the prior artdual-damascene integration scheme described above suffers from severaldrawbacks including: First, it constitutes a signification portion ofmanufacturing cost of advanced semiconductor chips as many layers, up totwelve layers for the state-of-the-art chips, are required to connectthe minuscule transistors within a chip and to the printed circuitboard. Second, it is a main yield detractor as the many layers of filmsrequired to form the interconnects generate chances for defectintroduction and, thus, degrade manufacturing yields. Third, it is veryinefficient and embodies enormous complexity. The current dual-damasceneintegration scheme requires many sacrificial films (80% of the filmstack) to pattern and protect the fragile interlayer dielectric filmsfrom damage during processing. These sacrificial patterning andprotective films have to be removed after patterning and copper plating.Fourth, the performance gain by introduction of new lower-k materials isoften offset by the needs for higher-k non-sacrificial materials, suchas a cap layer, a hardmask layer, or a thicker copper barrier layer.Fifth, the prior art complex dual-damascene process lengthensmanufacturing turn-around time and R&D development cycle. Sixth, theplasma etching process is an expensive and often unreliable process andrequires significant up-front capital investment.

In view of the above, there is a need to simplify the formation ofinterconnects (single-damascene and dual-damascene) including low-kdielectrics for cost-saving and manufacturing efficiency.

SUMMARY

The problems described above in prior art processes of fabricatinginterconnect (single-damascene and dual-damascene) structures are solvedby using a dramatically simplified integration method of this invention.The present invention thus relates to a method of forming interconnectstructures that are a permanent part of integrated circuits andmicroelectronic devices with patternable low-k dielectrics combined witha graded cap layer. The graded cap layer, which is present between asubstrate and an overlying patternable low-k dielectric material,includes a lower region that functions as a barrier layer, and an upperregion that has properties of a permanent antireflective coating. Atleast one middle region is located between the upper ad lower regions ofthe graded cap layer. The graded cap layer described herein replaces amultilayered stack comprised of a dielectric cap and an antireflectivecoating (ARC) that is employed in prior processes integrating apatternable low-k material. The graded cap layer described hereinprovides a simpler film stack and thus solves profile degradationproblem during an ARC/cap open process in the multilayered stackemployed in prior art processes. Furthermore, a thinner graded cap layerdescribed herein reduces the plasma etch process time used to open thecap layer, thus reducing potential plasma damage to the patternablelow-k material.

The invention described herein also circumvents the prior art drawbacksof traditional BEOL integration by combining the functions of aphotoresist and a dielectric material into one single material. This onematerial, called a photo-patternable low-k dielectric (or patternablelow-k material for short), acts as a photoresist during the lithographicpatterning process, and as such, no separate photoresist is required.After lithographic patterning, the patternable low-k dielectric issubsequently converted into a low-k material during a post patterningcure. In this way, the inventive method avoids plasma etching of low-kdielectric materials and the complex sacrificial film stack andprocesses required for patterning of low-k dielectric materials.

In one embodiment of the present invention, an interconnect structure isprovided that includes at least one patterned and cured low-k materiallocated directly on a surface of a patterned graded cap layer. The atleast one patterned and cured low-k material and the patterned gradedcap layer each have conductively filled regions embedded therein. Thepatterned and cured low-k material comprises a cured product of apatternable composition comprising a functionalized polymer, copolymer,or a blend including at least two of any combination of polymers and/orcopolymers having one or more photo/acid-sensitive imageable groups. Thegraded cap layer includes a lower region that functions as a barrierlayer and an upper region that has properties of a permanentantireflective coating. At least one middle region is located betweenthe upper and lower regions. The at least one middle region is formedfrom a combination of precursors used in forming the upper and lowerregions of the graded cap layer.

In another embodiment of the present invention, a dual-damasceneinterconnect structure is provided that includes a lower patterned andcured low-k material located directly on a patterned graded cap layerand an abutting upper patterned and cured low-k material located on thelower patterned and cured low-k material. The lower and upper patternedand cured low-k materials as well as the patterned graded cap layer eachhave conductively filled regions embedded therein. The patterned andcured upper and lower low-k materials are cured products of a same ordifferent patternable composition comprising a functionalized polymer,copolymer, or a blend including at least two of any combination ofpolymers and/or copolymers having one or more photo/acid-sensitiveimageable groups. The graded cap layer includes a lower region thatfunctions as a barrier layer and an upper region that has properties ofa permanent antireflective coating. At least one middle region islocated between the upper and lower regions of the graded cap layer.

In another embodiment of the invention, an air-gap containingdual-damascene interconnect structure is provided that includes at leastone airgap located within at least one patterned and cured patternablelow-k material adjacent, but not directly abutting conductively filledregions also located within the at least one patterned and curedpatternable low-k material.

In another embodiment of the invention, a method of fabricating aninterconnect structure is provided that includes providing at least onepatternable low-k material directly on a surface of graded cap layer.The at least one patternable low-k material is a patternable compositioncomprising a functionalized polymer, copolymer, or a blend including atleast two of any combination of polymers and/or copolymers having one ormore photo/acid-sensitive imageable groups, and the graded cap layerincludes a lower region that functions as a barrier layer and an upperregion that has properties of a permanent antireflective coating. Atleast one middle region is located between the upper and lower regionsof the graded cap layer. At least one interconnect pattern is formedwithin the at least one patternable low-k material and the graded caplayer. The at least one interconnect pattern is formed without utilizinga separate photoresist material. The at least one patterned patternablelow-k material is cured into a cured dielectric material having adielectric constant of not more than 4.3. The at least one interconnectpattern is filled with an electrically conductive material.

In yet another embodiment of the invention, a method of fabricating adual-damascene interconnect structure is provided that includesproviding a first patternable low-k material directly on a surface of agraded cap layer. The first patternable low-k material is a patternablecomposition comprising a functionalized polymer, copolymer, or a blendincluding at least two of any combination of polymers and/or copolymershaving one or more photo/acid-sensitive imageable groups, and the gradedcap layer includes a lower region that functions as a barrier layer andan upper region that has properties of a permanent antireflectivecoating. At least one middle region is located between the upper andlower regions of the graded cap layer. First interconnect patterns areformed within the first patternable low-k material without a separatephotoresist. A second patternable low-k material is provided on top ofthe first patterned low-k material having the first interconnectpatterns. The second patternable low-k material has a same or differentpatternable composition as the first patternable low-k material. Secondinterconnect patterns are formed within the second patternable low-kmaterial without a separate photoresist. A post patterning cure isapplied to the first and the second patterned patternable low-kmaterials to convert them into cured low-k dielectric material ormaterials. At least one opening is provided in exposed portions of thegraded cap layer, and the first and the second interconnect patterns andthe opening within the graded cap layer are filled with an electricallyconductive material.

In yet another embodiment of the invention, a method of fabricating adual-damascene interconnect structure is provided as above except thatthe post patterning cure is applied after at least one opening has beenprovided in exposed portions of the graded cap layer, and the first andthe second interconnect patterns and before the opening of the first andthe second patternable low-k materials and the graded cap layer isfilled with an electrically conductive material.

In yet another embodiment of the invention, a method of fabricating anair-gap containing dual-damascene interconnect structure is providedafter forming the standard metal filled dual-damascene interconnectstructure.

It is observed that the patternable low-k material used in the presentinvention becomes a permanent element of the interconnect structureafter a curing step has been performed. It is also observed that thegraded cap layer used in the present invention becomes a permanentelement of the interconnect structure too.

DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a pictorial representation (through a cross sectional view)illustrating an initial structure that is employed in one embodiment ofthe invention including a graded cap layer located on a surface of asubstrate.

FIG. 2 is a pictorial representation (through a cross sectional view) ofthe structure shown in FIG. 1 after forming a first patternable low-kmaterial directly on an upper surface of the graded cap layer.

FIG. 3 is a pictorial representation (through a cross sectional view) ofthe structure shown in FIG. 2 after formation of a via pattern withinthe first patternable low-k material.

FIG. 4 is a pictorial representation (through a cross sectional view) ofthe structure shown in FIG. 3 after forming a second patternable low-kmaterial over the entire surface of that structure.

FIG. 5 is a pictorial representation (through a cross sectional view) ofthe structure shown in FIG. 4 after forming a trench pattern within thesecond patternable low-k material and recovering the via within thefirst patternable low-k material.

FIG. 6 is a pictorial representation (through a cross sectional view) ofthe structure shown in FIG. 5 after curing of the patterned first andpatterned second patternable low-k materials and opening of the gradedcap layer.

FIG. 7 is a pictorial representation (through a cross sectional view) ofthe structure shown in FIG. 6 after conductive fill and planarization.

FIG. 8 is a pictorial representation (through a cross sectional view) ofthe structure shown in FIG. 8 after forming another graded cap layeratop the exposed surfaces thereof.

FIG. 9 is a pictorial representation (through a cross sectional view) ofthe structure shown in FIG. 9 after further processing in which at leastone airgap is formed within the structure.

FIG. 10 is a pictorial representation (through a cross sectional view)of a single-damascene structure that can be formed utilizing thestructure shown in FIG. 2 and subjecting that structure to interconnectpatterning, conductive fill, and planarization.

DETAILED DESCRIPTION

The present invention, which provides interconnect structures includinga patternable low-k material and a graded cap layer that serves as botha dielectric cap and an antireflective coating (ARC) and methods offabricating such interconnect structures, will now be described ingreater detail by referring to the following discussion and drawingsthat accompany the present application. It is noted that the drawingsthat accompany the present application are provided for illustrativepurposes only, and, as such, these drawings are not drawn to scale.

The invention disclosed herein circumvents profile degradation andplasma damage problems of prior art interconnect structure that areformed from a patternable low-k dielectric by utilizing a graded caplayer instead of a separate multilayered stack that includes adielectric cap and an overlying ARC. Additionally, this inventioncircumvents the prior art drawbacks of traditional interconnectintegration by using a patternable low-k material, which combines thefunctions of a photoresist and a dielectric material into one material.This patternable low-k material acts as a photoresist during thelithographic patterning process and, as such a separate photoresist isnot required or used. It is noted that the patternable low-k materialsemployed are any materials possessing two functions; they act as aphotoresist during a patterning process and are subsequently convertedinto a low-k dielectric during a post patterning cure process. The curedproduct of a patternable low-k material, therefore, can serve as apermanent on-chip dielectric insulator. The patternable low-k materialcan be deposited from a liquid phase or a gas phase. The terms “cure” or“curing” are used interchangeable to refer one of the processes selectedfrom a thermal cure, an electron beam cure, an ultra-violet (UV) cure,an ion beam cure, a plasma cure, a microwave cure or a combinationthereof. A “cured” product of a patternable low-k material is theproduct of the patternable low-k material after it has undergone one ofthe aforementioned cure processes. The “cured” product of a patternablelow-k material is different from the patternable low-k material inchemical nature and physical, mechanical and electrical properties.

One embodiment of the present invention will now be described inreference to FIGS. 1-8 which illustrate a preferred embodiment in whicha dual-damascene interconnect structure including cured patternablelow-k materials and a graded cap layer is formed. Although thispreferred embodiment is described and illustrated, the method can beadopted to form single-damascene interconnect structures as well; SeeFIG. 10.

FIG. 1 illustrates an initial structure 10 that is utilized, whichincludes a substrate 12 and a graded cap layer 14 located on a surfaceof substrate 12. The substrate 12 may comprise a semiconductingmaterial, an electrically insulating material, an electricallyconductive material, devices or structures made of these materials orany combination thereof (e.g., a lower level of an interconnectstructure). When the substrate 12 is comprised of a semiconductingmaterial, any semiconductor such as Si, SiGe, SiGeC, SiC, Ge alloys,GaAs, InAs, InP and other III/V or II/VI compound semiconductors, ororganic semiconductors may be used. The substrate 12 may also be aflexible substrate containing devices that are suitable for high-speedroll-to-roll processing. In addition to these listed types ofsemiconducting materials, substrate 12 may also be a layeredsemiconductor such as, for example, Si/SiGe, Si/SiC,silicon-on-insulators (SOIs) or silicon germanium-on-insulators (SGOIs).These semiconductor materials may form a device, or devices orstructures, which may be discrete or interconnected. These devices anddevice structures may be for computation, transmission, storage ordisplay of information, such as logic devices, memory devices, switchesor display devices.

When the substrate 12 is an electrically insulating material, theinsulating material can be an organic insulator, an inorganic insulatoror a combination thereof including multilayers. The substrate 12 canalso include a patternable low-k dielectric material as well. Theseelectrically insulating materials may be part of a device, or devices orstructures, which may be discrete or interconnected. These devices andstructures may be for logic applications or memory applications.

When the substrate 12 is an electrically conducting material, thesubstrate may include, for example, polySi, an elemental metal, an alloyincluding at least one elemental metal, a metal silicide, a metalnitride or combinations thereof including multilayers. When thesubstrate 12 comprises a semiconducting material, one or moresemiconductor devices such as, for example, complementary metal oxidesemiconductor (CMOS) devices, strained silicon devices, carbon-based(e.g., carbon nanotubes and/or graphene) devices, phase-change memorydevices, magnetic memory devices, magnetic spin switching devices,single electron transistors, quantum devices, molecule-based switchesand other switching or memory devices that can be part of an integratedcircuit, can be fabricated thereon.

The graded cap layer 14 that is formed directly on the surface ofsubstrate 12 includes a lower region 14A and an upper region 14B; atleast one middle, i.e., transition, region 14C can be present betweenthe upper and lower regions. This at least one middle region 14C isformed by using different ratios of the precursors used in forming thelower region 14A and the upper region 14B. As such, the grading incomposition within the graded cap layer is along the vertical directionrelative to a surface of substrate 12.

The inventive graded cap layer 14 performs and enhances two essentialfunctions for the integration of patternable low-k materials: anantireflective coating (ARC) function by the upper region 14B and a Cubarrier (cap) layer function by the lower region 14A. Since these twofunctions are imparted into the graded cap layer 14, the thickness ofthe graded cap layer 14 can be less than the combined thickness of thetwo separate ARC and cap layers. Moreover, this graded cap layer 14eliminates the interface of the two layer structure. Therefore potentialadhesion issues in the two layer structure can be avoided.

The upper region 14B of the graded cap layer should have the followinggeneral ARC characteristics: (i) It acts as an antireflective coating(ARC) during a lithographic patterning process. (ii) It withstandshigh-temperature BEOL integration processing (up to 500° C.); (iii) Itprevents resist (e.g., the patternable low-k material) poisoning by thesubstrate; (iv) It provides vertical wall profile and sufficient etchselectivity between the patternable low-k material and the ARC layer;(v) It serves as a permanent dielectric layer in a chip (low dielectricconstant, preferably k<5, more preferably k<3.6); and (vi) It iscompatible with conventional BEOL integration and produces reliablehardware.

The lower region 14A of the graded cap layer should have the followinggeneral cap characteristics. That is, the lower region 14A of the gradedcap layer 14 has properties of a dielectric cap: (1) It acts as aneffective Cu diffusion barrier to prevent any adverse effect ofdiffusion of any chemicals that will degrade the electrical conductivityand reliability of the conductor, such as Cu or Cu alloys; (2) Itenhances the electromigration reliability performance of the resultantinterconnect structure or device; (3) It should provide at leastadequate adhesion with its adjacent layers during the fabricationprocess and reliability testing. The lower region 14A of the graded caplayer 14 can comprise atoms of any dielectric cap material includingatoms of Si and C; Si and N; Si and O; Si, O and N; atoms of Si, C andO; Si, C, O and H; and Si, C, N and H. Additionally, the lower region14A of the graded cap 14 may include atoms of Ru, Co, W and P.

The graded cap layer 14 is formed utilizing a conventional gas phasedeposition process such as, for example, chemical vapor deposition(CVD), plasma enhanced chemical vapor deposition (PECVD), and atomiclayer deposition (ALD). In some embodiments, a liquid phase depositionprocess can be used in forming a portion of the graded cap layer 14. Informing the graded cap layer 14, a first precursor, i.e., a dielectriccap precursor, is used in forming the lower region of the graded caplayer, while a second precursor, i.e., an ARC precursor, is used informing the upper region of the graded cap layer. In one embodiment, thegraded cap layer is formed by at least three discrete layers: a bottomlayer that uses a cap precursor and a top layer that uses an ARCprecursor and a middle layer that employs a mixture of both precursors.In another embodiment, the graded cap layer is a continuous layer withgradually varied composition along the vertical direction. This type ofgraded cap layer is formed by using both precursors at the same time andthe various regions are formed by gradually altering the ratios of thetwo precursors.

The graded cap layer 14 typically has a thickness 2 nm to 200 nm, with athickness from 10 nm to 100 nm being more typical.

The upper region 14B of the graded cap layer 14 has antireflectivecoating properties as described above. Further discussion is nowprovided for characteristics (i)-(v) of the upper region 14B of gradedcap 14.

Characteristic (i), i.e., the upper region 14B of the graded cap layer14 acts as an antireflective coating (ARC) during a lithographicpatterning process: The upper region 14B of the graded cap layer 14 maybe designed to control reflection of light that is transmitted throughthe patternable low-k material (to be subsequently formed), reflectedoff the substrate and back into the patternable low-k material, where itcan interfere with incoming light and cause the patternable low-kmaterial to be unevenly exposed (along the vertical direction). Theoptical constant of the upper region 14B of the graded cap layer 14 isdefined here as the index of refraction n and the extinction coefficientk. In general, the upper region 14B of the graded cap layer 14 can bemodeled so as to find optimum optical parameters (n and k values) of anARC as well as optimum thickness. The preferred optical constants of theupper region 14B of the graded cap layer 14 are in the range from n=1.2to n=3.0 and k=0.01 to k=0.9, preferably n=1.4 to n=2.6 and k=0.02 tok=0.78 at a wavelength of 365, 248, 193 and 157, 126 nm and extremeultraviolet (13.4 nm) radiation. The optical properties and thickness ofthe upper region 14B of the graded cap layer 14 are optimized to obtainoptimal resolution and profile control of the patternable low-k materialduring the subsequent patterning steps, which is well known to thoseordinarily skilled in the art.

Characteristic (ii), i.e., the upper region 14B of the graded cap layer14 can withstand high-temperature BEOL integration processing (up to500° C.): The graded cap layer 14, particularly the upper region 14B,must withstand the harsh processing conditions during BEOL integration.These include high temperature and intense UV curing. The processtemperature can be as high as 450° C. The intensity of the light used inthe UV cure process can be as high as tens of J/cm².

Characteristic (iii), i.e., the upper region 14B of the graded cap layer14 prevents resist (e.g., patternable low-k material) poisoning by thesubstrate: The patternable low-k materials employed are preferablychemically amplified resists. They can be poisoned by any basiccontaminant from the underlying substrate 12 or from the lower region14A of the graded cap layer. As such, the upper region 14B of the gradedcap layer 14 must serve as an additional barrier layer to prevent basiccontaminant from the underlying substrate from diffusing into thepatternable low-k material to poison the chemically amplifiedpatternable low-k material.

Characteristic (iv), i.e., The upper region 14B of the graded cap layer14 provides vertical wall profile and sufficient etch selectivitybetween the patternable low-k material and the graded cap layer 14: Theupper region 14B of the graded cap layer 14 should provide sufficientreflectivity control with reflectivity from the underlying substrateunder a particular lithographic wavelength of less than 8%, preferablyless than 5%, more preferably less than 2% and generate vertical sidewafer profile. The upper region 14B of the graded cap layer 14 shouldalso generate residue-free patterns with no footing. Moreover, theadhesion of the patternable low-k material should be sufficient toprevent pattern collapse during patterning and a subsequent UV cure. Theupper region 14B of the graded cap layer 14 should also be designed suchthat the etch selectivity during graded cap open process is sufficientlyhigh so that the opening of the graded cap stack does not erodesignificant portion of the patternable low-k material and degradesignificantly its pattern profile. An etch selectivity (etch rate ratioof graded cap versus patternable low-k material) is greater than 1,preferably greater than 3, more preferable greater than 5.

Characteristic (v), i.e., the upper region 14B of the graded cap layer14 serves as a permanent dielectric layer in a chip: The graded caplayer 14 including the upper region 14B and the lower region 14A remainsafter patterning and cure of the patternable low-k material. It servesas a permanent dielectric layer in a chip. Therefore, the graded caplayer 14 including the upper region 14B (after cure) must meet therequirements of an on-chip dielectric insulator, including electricalproperties (low dielectric constant: preferably k less than 5, and morepreferably k less than 3.6; dielectric breakdown field: greater than 2MV/cm, preferably greater than 4 MV/cm, and more preferably greater than6 MV/cm, leakage: less than 10⁻⁵ A/cm², preferably less than 10⁻⁷ A/cm²,and more preferably less than 10⁻⁹ A/cm²); mechanical properties(adhesion energy is equal to or greater than the cohesive energy of theweakest layer of the integrated film stack); must pass electrical andmechanical reliability tests.

The upper region 14B of the graded cap layer 14 may include atoms thatare associated with inorganic antireflective coatings, such as, forexample, atoms of Si, C, O, N and H, atoms of Si and C, atoms of Si, Oand C, atoms of Si, C, O and H, atoms of W, Co, Ru, Ta, Ti, and Ru andthe like.

In one embodiment, the upper region 14B of the graded cap layer 14 is aninorganic composition that includes atoms of M, C (carbon) and H(hydrogen), wherein M is selected from at least one atom of Si, Ge, B,Sn, Fe, Ta, Ti, Ni, Hf and La. This inorganic composition may optionallyinclude atoms of O, N, S, F or mixtures thereof. In some embodiments, Mis preferably Si. In some embodiments, this inorganic composition mayalso be referred to as a vapor deposited M:C:H:optionally X material,wherein M is as defined above, and X is at least one element of O, N, Sand F.

In another embodiment, the graded cap layer is a graded silicon carbidenitride film deposited by PECVD method. To synthesize the graded siliconcarbide nitride film, a combination of reactant gases: a silicon source,a carbon source, and a nitrogen source is necessary. Additionally thereactant gases must be introduced in varying stoichiometries to achievethe necessary properties. The gas mixture may also comprise an inertcarrier gas such as helium or argon.

Within the present invention, the silicon containing precursor of aninorganic composition comprises any Si containing compound includingmolecules selected from silane (SiH₄) derivatives having the molecularformulas SiR₄, cyclic Si containing compounds including cyclocarbosilanewhere the R substitutents may or may not be identical and are selectedfrom H, alkyl, phenyl, vinyl, allyl, alkenyl or alkynyl groups that maybe linear, branched, cyclic, polycyclic and may be functionalized withnitrogen containing substituents, any cyclic Si containing compoundsincluding cyclosilanes, cyclocarbosilanes.

Preferred silicon precursors include, but are not limited to: silane,methylsilane, dimethylsilane, trimethylsilane, tetramethylsilane,ethylsilane, diethylsilane, triethylsilane, tetraethylsilane,ethylmethylsilane, triethylmethylsilane, ethyldimethylsilane,ethyltrimethylsilane, diethyldimethylsilane,1,1,3,3-tetrahydrido-1,3-disilacyclobutane; 1,3-disilacyclobutane;1,3-dimethyl-1,3-dihydrido-1,3-disilylcyclobutane; 1,1,3,3,tetramethyl-1,3-disilacyclobutane;1,1,3,3,5,5-hexahythido-1,3,5-trisilane;1,1,3,3,5,5-hexamethyl-1,3,5-trisilane;1,1,1,4,4,4-hexahydrido-1,4-disilabutane; and 1,4-bis-trihydrosilylbenzene. Also the corresponding meta substituted isomers, such asdimethyl-1-propyl-3-silabutane; 2-silapropane, 1,3-disilacyclobutane,1,3-disilapropane, 1,5-disilapentane, or 1,4-bis-trihydrosilyl benzene.

A single precursor such as silane amine, Si(Net)₄, can be used as thesilicon, carbon and nitrogen source. Another preferred method is amixture of precursors, a silicon containing source such as silane,disilane, or an alkylsilane such as tetramethylsilane, ortrimethylsilane, and a nitrogen containing source such as ammonia,amines, nitriles, aminos, azidos, azos, hydrizos. An additional carbonsource and/or carbon and nitrogen containing source comprised of alinear, branched, cyclic or polycyclic hydrocarbon backbone of—[CH₂]_(n)—, where n is greater than or equal to 1, and may besubstituted by functional groups selected from alkenes (—C═C—), alkynes(—C≡C—), amines (—C—N—), nitriles (—C≡N), amino (—NH2), azido (—N═N═N—)and azo (—N═N—) may also be required. Within the invention, thehydrocarbon backbone may be linear, branched, or cyclic and may includea mixture of linear branched and cyclic hydrocarbon moieties. Theseorganic groups are well known and have standard definitions that arealso well known in the art. These organic groups can be present in anyorganic compound.

The method of the present invention may further comprise the step ofproviding a parallel plate reactor, which has an area of a substratechuck from about 85 cm² to about 750 cm², and a gap between thesubstrate and a top electrode from about 1 cm to about 12 cm. A highfrequency RF power is applied to one of the electrodes at a frequencyfrom about 0.45 MHz to about 200 MHz. Optionally, an additional RF powerof lower frequency than the first RF power can be applied to one of theelectrodes. A single source precursor or a mixture of precursors whichprovide a silicon, carbon and nitrogen source are introduced into areactor.

The conditions used for the deposition step may vary depending on thedesired final properties of a graded SiCN(H) film. Broadly, theconditions used for providing a SiCN(H) comprising elements of Si, C, N,H, include: setting the substrate temperature within a range from about100° C. to about 700° C.; setting the high frequency RF power densitywithin a range from about 0.1 W/cm² to about 2.0 W/cm²; setting the gasflow rates within a range from about 5 sccm to about 10000 sccm, settingthe inert carrier gases, such as helium (or/and argon) flow rate withina range from about 10 sccm to about 10000 sccm; setting the reactorpressure within a range from about 1 Torr to about 10 Torr; and settingthe high frequency RF power within a range from about 10 W to about 1000W. Optionally, a lower frequency power may be added to the plasma withina range from about 10 W to about 600 W. When the conductive area of thesubstrate chuck is changed by a factor of X, the RF power applied to thesubstrate chuck is also changed by a factor of X. Gas flows of silane,carbon and/or nitrogen gas precursors are flowed into the reactor at aflow rate within a range from about 10 sccm to about 1000 sccm.

While gas precursors are used in the above example, liquid precursorsmay also be used for the deposition.

An example of the first method of the present invention is now describedto make a SiCNH material: A 200 mm substrate is placed in a PECVDreactor on a heated wafer chuck at 200°-600° C. Any PECVD depositionreactor may be used within the present invention. Gas and liquidprecursor flows are then stabilized to reach a pressure in the rangefrom 1-10 Torr, and RF radiation is applied to the reactor showerheadfor a time from about 5 to about 500 seconds.

In one preferred embodiment, the upper region 14B of graded cap layer 14includes atoms of Si:C:H:X. These Si containing materials are depositedfrom at least one Si containing precursor. More particularly, theSi:C:H:X materials are deposited from at least one Si containingprecursor with, or without, additions of nitrogen and/or oxygen and/orfluorine and/or sulfur containing precursors. The Si containingprecursor that is employed may comprise any Si containing compoundincluding molecules selected from silane (SiH₄) derivatives having themolecular formulas SiR₄, cyclic Si containing compounds includingcyclocarbosilane where the R substitutents may or may not be identicaland are selected from H, alkyl, phenyl, vinyl, allyl, alkenyl or alkynylgroups that may be linear, branched, cyclic, polycyclic and may befunctionalized with nitrogen containing substituents, any cyclic Sicontaining compounds including cyclosilanes, and cyclocarbosilanes.Preferred silicon precursors include, but are not limited to silane,methylsilane, dimethylsilane, trimethylsilane, tetramethylsilane,ethylsilane, diethylsilane, triethylsilane, tetraethylsilane,ethylmethylsilane, triethylmethylsilane, ethyldimethylsilane,ethyltrimethylsilane, diethyldimethylsilane,1,1,3,3-tetrahydrido-1,3-disilacyclobutane; 1,3-disilacyclobutane;1,3-dimethyl-1,3-dihydrido-1,3-disilylcyclobutane;1,1,3,3,tetramethyl-1,3-disilacyclobutane;1,1,3,3,5,5-hexahydrido-1,3,5-trisilane;1,1,3,3,5,5-hexamethyl-1,3,5-trisilane;1,1,1,4,4,4-hexahydrido-1,4-disilabutane; and 1,4-bis-trihydrosilylbenzene. Also the corresponding meta substituted isomers, such asdimethyl-1-propyl-3-silabutane; 2-silapropane, 1,3-disilacyclobutane,1,3-disilapropane, 1,5-disilapentane, or 1,4-bis-trihydrosilyl benzenemay be employed.

A single precursor such as silane amine, Si(Net)₄, can be used as thesilicon, carbon and nitrogen source. Another preferred method is amixture of precursors, a silicon containing source such as silane,disilane, or a alkylsilane such as tetramethylsilane, ortrimethylsilane, and a nitrogen containing source such as ammonia,amines, nitriles, aminos, azidos, azos, hydrizos. An additional carbonsource and/or carbon and nitrogen containing source comprised of alinear, branched, cyclic or polycyclic hydrocarbon backbone of—[CH₂]_(n)—, where n is greater than or equal to 1, and may besubstituted by functional groups selected from alkenes (—C═C—), alkynes(—C≡C—), amines (—C—N—), nitriles (—C≡N), amino (—NH2), azido (—N═N═N—)and azo (—N═N—) may also be required. The hydrocarbon backbone may belinear, branched, or cyclic and may include a mixture of linear branchedand cyclic hydrocarbon moieties. These organic groups are well known andhave standard definitions that are also well known in the art. Theseorganic groups can be present in any organic compound.

The atomic % ranges for M in such materials are as follows: preferably0.1 atomic % to 95 atomic %, more preferably 0.5 atomic % to 95 atomic%, most preferably 1 atomic % to 60 atomic % and most highly preferably5 atomic % to 50 atomic %. The atomic % ranges for C in the upper region14B are as follows: preferably 0.1 atomic % to 95 atomic %, morepreferably 0.5 atomic % to 95 atomic %, most preferably 1 atomic % to 60atomic % and most highly preferably 5 atomic % to 50 atomic %. Theatomic % ranges for H in the upper region 14B are as follows: preferably0.1 atomic % to 50 atomic %, more preferably 0.5 atomic % to 50 atomic%, most preferably 1 atomic % to 40 atomic % and most highly preferably5 atomic % to 30 atomic %. The atomic % ranges for X in the upper region14B are as follows: preferably O atomic % to 70 atomic %, morepreferably 0.5 atomic % to 70 atomic %, most preferably 1 atomic % to 40atomic % and most highly preferably 5 atomic % to 30 atomic %.

The upper region 14B of graded cap layer 14 including atoms of M, C andH has a tunable index of refraction and extinction coefficient which canbe optionally graded along the film thickness to match the opticalproperties of the substrate and the patternable low-k material. Theoptical properties and the lithographic features of the upper region 14Bof the graded cap layer 14 are vastly superior to those obtained by theprior art.

It should be noted that by changing process parameters such as biasvoltage, gas mixture, gas flow, pressure and deposition temperature, theoptical constant of the upper region 14B of the graded cap layer 14 canbe changed. In addition, the composition of the starting precursor aswell as the introduction of oxygen, nitrogen, fluorine, and sulfurcontaining precursors also allows the tunability of these films. Theoptical constants of the upper region 14B of graded cap layer 14 aredefined here as the index of refraction n and the extinction coefficientk.

In another embodiment, upper region 14B of graded cap layer 14 is formedby a liquid deposition process including for example, spin-on coating,spray coating, dip coating, brush coating, evaporation or chemicalsolution deposition. This liquid deposited upper region 14B is formed byeither depositing a film with ARC properties on a lower region 14A ofthe graded layer or by forming graded cap layer with a mixturecomprising an ARC-like component through phase separation. This upperregion 14B of graded cap layer 14 formed by liquid deposition comprisesa polymer that has at least one monomer unit comprising the formulaM-R^(A) wherein M is at least one of the elements of Si, Ge, B, Sn, Fe,Ta, Ti, Ni, Hf and La and R^(A) is a chromophore. Such an ARC isdescribed in U.S. Patent Publication No. 2009/0081418 the entire contentof which is incorporated herein by reference. In some embodiments, Mwithin the monomer unit may also be bonded to organic ligands includingelements of C and H, a cross-linking component, another chromophore ormixtures thereof. The organic ligands may further include one of theelements of O, N, S and F. When the organic ligand is bonded to M, it isbonded to M′ through C, O, N, S, or F.

In other embodiments, the upper region 14B of graded cap layer 14 formedby liquid deposition may also include at least one second monomer unit,in addition to the at least one monomer unit represented by the formulaM-R^(A). When present, the at least one second monomer unit has theformula M′-RB, wherein M′ is at least one of the elements of Si, Ge, B,Sn, Fe, Ta, Ti, Ni, Hf and La, and R^(B) is a cross-linking agent. M andM′ may be the same or different elements. In these two formulae, M andM′ within the monomer unit may be also be bonded to organic ligandsincluding atoms of C and H, a cross-linking component, a chromophore ormixtures thereof. The organic ligands may further include one of theelements of O, N, S and F. When the organic ligand is bonded to M andM′, it is bonded to M or M′ through C, O, N, S, or F.

The liquid composition comprising M-R^(A) or M-R^(A) and M′-R^(B) mayalso comprise at least one additional component, including a separatecrosslinker, an acid generator or a solvent.

When liquid deposition is employed, upper region 14B of graded cap layer14 is formed by liquid phase deposition of a liquid composition thatincludes an inorganic precursor that includes element of M, C and H,wherein M is at least one of the elements of Si, Ge, B, Sn, Fe, Ta, Ti,Ni, Hf and La. The inorganic precursor used in forming the upper region14B may optionally include elements of O, N, S, F or mixtures thereof.In some embodiments, M is preferably Si. The liquid composition alsoincludes, in addition to the inorganic precursor, a chromophore, across-linking component, an acid generator and solvent.

One embodiment of the inorganic composition used in the liquiddeposition embodiment comprises M-R^(A) and M′-R^(B) units, wherein Mand M′ is at least one of the elements of Si, Ge, B, Sn, Fe, Ta, Ti, Ni,Hf and La or is selected from Group IIIB to Group VIB, Group IIIA, andGroup IVA. The inorganic precursor used in forming the upper region 14Bmay optionally include elements of O, N, S, F or mixtures thereof. Oneembodiment of the upper region 14B composition comprises the MO_(y) unitwhich can be any one of many different metal-oxide forms. An exemplarylist of such metal-oxide forms for a particular metal is as follows:MO₃; wherein M is Sc, Y, lanthanide, and Group IIIA; B, Al, Ga or In;MO₄; wherein M is Group IVB; Ti, Zr or Hf, and Group IVA; Sn or Ge; MO₅;wherein M is Group VB; V, Nb or Ta; or P. The Group VB metals are alsoknown to form stable metal oxo forms, LMO3, wherein L is an oxo; LMO;many of the listed metals form stable acetoacetato-metal complexes; LMO;many of the listed metals form stable cyclopentadienyl-metal complexes;LMO; wherein L is an alkoxy ligand; M is Sc, Y, or lanthanide, GroupIVB, and Group VB; or LMO; wherein L is an alkyl or phenyl ligand; M isGroup IIIA or Group IVA.

The chromophore, cross-linking component and acid generator that can beused in the liquid deposited upper region 14B are defined in greaterdetail with respect to the following preferred embodiment of the presentinvention. In a preferred embodiment, the upper region 14B of graded caplayer 14 is formed by liquid deposition characterized by the presence ofa silicon-containing polymer having units selected from a siloxane,silane, carbosilane, oxycarbosilane, silsesquioxane,alkyltrialkoxysilane, tetra-alkoxysilane, or silicon-containing andpendant chromophore moieties. The polymer containing these units may bea polymer containing these units in the polymer backbone and/or inpendant groups. Preferably, the polymer contains the preferred units inits backbone. The polymer is preferably a polymer, a copolymer, a blendincluding at least two of any combination of polymers and/or copolymers,wherein the polymers include one monomer and the copolymers include atleast two monomers and wherein the monomers of the polymers and themonomer of the copolymers are selected from a siloxane, silane,carbosilane, oxycarbosilane, silsesquioxane, alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.

The polymer should have solution and film-forming characteristicsconducive to forming an ARC-type layer by conventional spin-coating. Inaddition to the chromophore moieties discussed below, thesilicon-containing polymer also preferably contains a plurality ofreactive sites distributed along the polymer for reaction with thecross-linking component.

Examples of suitable polymers include polymers having the silsesquioxane(ladder, caged, or network) structure. Such polymers preferably containmonomers having structures (I) and (II) below:

where R^(C) comprises a chromophore and R^(D) comprises a reactive sitefor reaction with the cross-linking component.

Alternatively, general linear organosiloxane polymers containingmonomers (I) and (II) can also be used. In some cases, the polymercontains various combinations of monomers (I) and (II) including linearstructures such that the average structure for R^(C)-containing monomersmay be represented as structure (III) below and the average structurefor R^(D)-containing monomers may be represented by structure (IV)below:

where x is from 1 to 1.5. In theory, x may be greater than 1.5, however,such compositions generally do not possess characteristics suitable forspin-coating processes (e.g., they form undesirable gel or precipitatephases).

Generally, silsesquioxane polymers are preferred. If the ordinaryorganosiloxane polymers are used (e.g., monomers of linear structures(I) and (III)), then preferably, the degree of cross-linking isincreased compared to formulations based on silsesquioxanes.

The chromophore-containing groups R^(C) (or R^(A) in the genericdescription above) may contain any suitable chromophore which (i) can begrafted onto the silicon-containing polymer (or M moiety of the genericmonomer defined above) (ii) has suitable radiation absorptioncharacteristics at the imaging wavelength, and (iii) does not adverselyaffect the performance of the layer or any overlying layers.

Preferred chromophore moieties include benzene and its derivatives,chrysenes, pyrenes, fluoranthrenes, anthrones, benzophenones,thioxanthones, and anthracenes. Anthracene derivatives, such as thosedescribed in U.S. Pat. No. 4,371,605 may also be used; the disclosure ofthis patent is incorporated herein by reference. In one embodiment,phenol, hydroxystyrene, and 9-anthracene methanol are preferredchromophores. The chromophore moiety preferably does not containnitrogen, except for possibly deactivated amino nitrogen such as inphenol thiazine.

The chromophore moieties may be chemically attached by acid-catalyzedO-alkylation or C-alkylation such as by Friedel-Crafts alkylation. Thechromophore moieties may also be chemically attached by hydrosilylationof SiH bond on the parent polymer. Alternatively, the chromophore moietymay be attached by an esterification mechanism. A preferred acid forFriedel-Crafts catalysis is HCl.

Preferably, 15 to 40% of the functional groups contain chromophoremoieties. In some instances, it may be possible to bond the chromophoreto the monomer before formation of the silicon-containing polymer. Thesite for attachment of the chromophore is preferably an aromatic groupsuch as a hydroxybenzyl or hydroxymethylbenzyl group. Alternatively, thechromophore may be attached by reaction with other moieties such ascyclohexanol or other alcohols. The reaction to attach the chromophoreis preferably an esterification of the alcoholic OH group.

R^(D) (or R^(B) in the generic description above) comprises a reactivesite for reaction with a cross-linking component. Preferred reactivemoieties contained in R^(D) are alcohols, more preferably aromaticalcohols (e.g., hydroxybenzyl, phenol, hydroxymethylbenzyl, etc.) orcycloaliphatic alcohols (e.g., cyclohexanoyl). Alternatively, non-cyclicalcohols such as fluorocarbon alcohols, aliphatic alcohols, aminogroups, vinyl ethers, and epoxides may be used.

Preferably, the silicon-containing polymer (before attachment of thechromophore) of a liquid deposited upper region 14B ispoly(4-hydroxybenzylsilsesquioxane). Examples of other silsesquioxanepolymers include: poly(p-hydroxyphenylethylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-p-hydroxy-alpha-methylbenzylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-methoxybenzylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-t-butylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-cyclohexylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-phenylsilsesquioxane),poly(p-hydroxyphenylethylsilsesquioxane-co-bicycloheptylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-p-hydroxybenzylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-methoxybenzylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-t-butylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-cyclohexylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-phenylsilsesquioxane),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-bicycloheptylsilsesquioxane),poly(p-hydroxybenzylsilsesquioxane-co-p-hydroxyphenylethylsilsesquioxane),andpoly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-alpha-methylbenzylsilsesquioxane).

The Si containing polymers that can be used in forming the liquiddeposited upper region 14B of graded cap layer 14 preferably have aweight average molecular weight, before reaction with the cross-linkingcomponent, of at least 1000, more preferably a weight average molecularweight of 1000-10000.

The cross-linking component of the liquid deposited upper region 14B ofgraded cap layer 14 is preferably a crosslinker that can be reacted withthe SiO containing polymer in a manner which is catalyzed by generatedacid and/or by heating. This cross-linking component can be inorganic ororganic in nature. It can be a small compound (as compared with apolymer or copolymer) or a polymer, a copolymer, or a blend including atleast two of any combination of polymers and/or copolymers, wherein thepolymers include one monomer and the copolymers include at least twomonomers. Generally, the cross-linking component used in the liquiddeposited antireflective compositions may be any suitable cross-linkingagent known in the negative photoresist art which is otherwisecompatible with the other selected components of the composition. Thecross-linking agents preferably act to crosslink the polymer componentin the presence of a generated acid. Preferred cross-linking agents areglycoluril compounds such as tetramethoxymethyl glycoluril,methylpropyltetramethoxymethyl glycoluril, andmethylphenyltetramethoxymethyl glycoluril, available under thePOWDERLINK trademark from American Cyanamid Company. Other possiblecross-linking agents include: 2,6-bis(hydroxymethyl)-p-cresol, compoundshaving the following structures:

including their analogs and derivatives, such as those found in JapaneseLaid-Open Patent Application (Kokai) No. 1-293339, as well as etherifiedamino resins, for example methylated or butylated melamine resins(N-methoxymethyl- or N-butoxymethyl-melamine respectively) ormethylated/butylated glycolurils, for example as can be found inCanadian Patent No. 1 204 547. Other cross-linking agents such asbis-epoxies or bis-phenols (e.g., bisphenol-A) may also be used.Combinations of cross-linking agents may be used. The cross-linkingcomponent may be chemically bonded to the Si containing polymerbackbone.

In another embodiment, the cross-linking component is asilicon-containing polymer having at least one unit selected from asiloxane, silane, carbosilane, oxycarbosilane, silsesquioxane,alkyltrialkoxysilane, and tetra-alkoxysilane. The polymer is preferablya polymer, a copolymer, a blend including at least two of anycombination of polymers and/or copolymers, wherein the polymers includeone monomer and the copolymers include at least two monomers and whereinthe monomers of the polymers and the monomers of the copolymers areselected from a siloxane, silane, carbosilane, oxycarbosilane,silsesquioxane, alkyltrialkoxysilane, tetra-alkoxysilane, unsaturatedalkyl substituted silsesquioxane, unsaturated alkyl substitutedsiloxane, unsaturated alkyl substituted silane, an unsaturated alkylsubstituted carbosilane, unsaturated alkyl substituted oxycarbosilane,carbosilane substituted silsesquioxane, carbosilane substitutedsiloxane, carbosilane substituted silane, carbosilane substitutedcarbosilane, carbosilane substituted oxycarbosilane, oxycarbosilanesubstituted silsesquioxane, oxycarbosilane substituted siloxane,oxycarbosilane substituted silane, oxycarbosilane substitutedcarbosilane, and oxycarbosilane substituted oxycarbosilane.

The acid generator used in the liquid deposited composition ispreferably an acid generator compound that liberates acid upon thermaltreatment. A variety of known thermal acid generators are suitablyemployed such as, for example, 2,4,4,6-tetrabromocyclohexadienone,benzoin tosylate, 2-nitrobenzyl tosylate and other alkyl esters oforganic sulfonic acids, blocked alkyl phosphoric acids, blockedperfluoroalkyl sulfonic acids, alkyl phosphoric acid/amine complexes,perfluoroalkyl acid quats wherein the blocking can be by covalent bonds,amine and quaternary ammonium. Compounds that generate a sulfonic acidupon activation are generally suitable. Other suitable thermallyactivated acid generators are described in U.S. Pat. Nos. 5,886,102 and5,939,236; the disclosures of these two patents are incorporated hereinby reference. If desired, a radiation-sensitive acid generator may beemployed as an alternative to a thermally activated acid generator or incombination with a thermally activated acid generator. Examples ofsuitable radiation-sensitive acid generators are described in U.S. Pat.Nos. 5,886,102 and 5,939,236. Other radiation-sensitive acid generatorsknown in the resist art may also be used as long as they are compatiblewith the other components of the antireflective composition. Where aradiation-sensitive acid generator is used, the cure (cross-linking)temperature of the composition may be reduced by application ofappropriate radiation to induce acid generation which in turn catalyzesthe cross-linking reaction. Even if a radiation-sensitive acid generatoris used, it is preferred to thermally treat the composition toaccelerate the cross-linking process (e.g., for wafers in a productionline).

The compositions used in the liquid deposition process preferablycontain (on a solids basis) (i) from 10 wt % to 98 wt. % of a polymerincluding M, more preferably from 70 wt. % to 80 wt. %, (ii) from 1 wt %to 80 wt. % of cross-linking component, more preferably from 3 wt. % to25%, most preferably from 5 wt. % to 25 wt. %, and (iii) from 1 wt. % to20 wt. % acid generator, more preferably 1 wt. % to 15 wt. %.

When the upper region 14B of graded cap layer 14 is formed by liquiddeposition process any liquid deposition process including for example,spin-on coating, spray coating, dip coating, brush coating, evaporationor chemical solution deposition can be used. After liquid depositing theupper region 14B, a post deposition baking step is typically, but notnecessarily always, used to remove unwanted components, such as solvent,and to effect crosslinking. When performed, the baking step is conductedat a temperature from 60° C. to 400° C., with a baking temperature from80° C. to 300° C. being even more preferred. The duration of the bakingstep varies and is not critical to the practice of the presentinvention. The baked and previously liquid deposited ARC 16 may furtherundergo a curing process. The curing is performed in the presentinvention by a thermal cure, an electron beam cure, an ultra-violet (UV)cure, an ion beam cure, a plasma cure, a microwave cure or anycombination thereof.

The lower region 14A of the graded cap layer 14 can comprise atoms ofany dielectric cap material including atoms of Si and C; Si and N; Siand O; Si, O and N; Si, C, O and H; and Si, C, N and H. Additionally,the lower region 14A of the graded cap layer 14 may include atoms of Ru,Co, W and P.

The lower region 14A of the graded gap later 14, which is formed priorto upper region 14B, can be formed utilizing a conventional depositionprocess such as, for example, chemical vapor deposition (CVD), plasmaenhanced chemical vapor deposition (PECVD), atomic layer deposition(ALD), chemical solution deposition, or evaporation. The precursors usedin forming the lower region 14A of the graded cap layer 14 include anyconventional precursor that can be used in forming a discrete dielectriccapping layer.

As stated above, the graded cap layer 14 can be formed by two generalmethods: (1) forming at least three discrete layers with the top layerbeing the ARC-like layer deposited with an ARC precursor or acombination of ARC precursors, the bottom layer the cap layer depositedwith a cap precursor or a combination of cap precursors, and at leastone middle layer with the combination of the ARC precursor and the capprecursor (2) forming a continuous layer with gradually variedcomposition along the vertical direction. Forming at least threediscrete layers can be achieved by depositing these layers in one singledeposition or a separate tool for each layer. Forming the continuousgraded cap layer can be achieved by gradually varying the ration of thecap precursor and the ARC precursor in the single tool with the lowerregions 14A comprising mostly the cap precursor and upper region 14Bcomprising mostly the ARC precursor.

In some embodiments, the as-deposited graded cap layer 14 may besubjected to a post deposition treatment to improve the properties ofthe entire layer or the surface of graded cap layer 14. This postdeposition treatment can be selected from heat treatment, irradiation ofelectromagnetic wave (such as ultra-violet light), particle beam (suchas an electron beam, or an ion beam), plasma treatment, chemicaltreatment through a gas phase or a liquid phase (such as application ofa monolayer of surface modifier) or any combination thereof. Thispost-deposition treatment can be blanket or pattern-wise. The postdeposition treatment enhances the chemical, physical, electrical, and/ormechanical properties of the graded cap layer 14 and/or the film stackcontaining graded cap layer 14, such as adhesion strength. The chemicalproperties include nature and/or location of surface functional groups,and hydrophilicity. The physical properties include density, moistureabsorption, and heat conductivity. The mechanical properties includemodulus, hardness, cohesive strength, toughness, resistance to crack andadhesion strength to its neighboring layers. The electrical propertiesinclude dielectric constant, electrical breakdown field, and leakagecurrent.

The heat treatment should be no higher than the temperature that theunderlying substrate can withstand, usually 500° C. This heat treatmentcan be conducted in an inert environment or within a chemicalenvironment in a gas phase or a liquid phase. This treatment step may ormay not be performed in the same tool as that used in forming graded caplayer 14.

The post deposition treatment by irradiation of electromagnetic wave canbe by ultra-violet (UV) light, microwave and the like. The UV light canbe broadband with a wavelength range from 100 nm to 1000 nm. It can alsobe UV light generated by an excimer laser or other UV light source. TheUV treatment dose can be a few mJ/cm² to thousands of J/cm². Thisirradiation treatment can be conducted at ambient temperature or at anelevated temperature no higher than 500° C. This irradiation treatmentcan be conducted in an inert environment or within a chemicalenvironment in a gas phase or a liquid phase. In one embodiment, thefollowing conditions may be employed: a radiation time from 10 sec to 30min, a temperature from room temperature to 500° C., and an environmentincluding vacuum, or gases such as, for example, inert gas, N₂, H₂, O₂,NH₃, hydrocarbon, and SiH₄. This treatment step may or may not beperformed in the same tool as that used in forming the graded cap layer14.

The post deposition treatment by plasma treatment can be selected fromoxidizing plasma, reducing plasma or a neutral plasma. Oxidizing plasmasinclude, for example, O₂, CO, and CO₂. Reducing plasmas include, forexample, H₂, N₂, NH₃, and SiH₄. The neutral plasmas include, forexample, Ar and He. A plasma treatment time from 1 sec to 10 min and aplasma treatment temperature from room temperature to 400° C. can beemployed. This treatment step may or may not be performed in the sametool as that used in forming the graded cap layer 14.

The post deposition chemical treatment may be conducted in a gas phaseor a liquid phase. In one embodiment, the following conditions may beemployed: a treatment time from 1 sec to 30 min, a temperature from roomtemperature to 500° C. Chemicals suitable for this chemical treatmentmay be selected from any chemicals that improve chemical, physical,electrical, and/or mechanical properties of graded cap layer 14 such asadhesion strength. This chemical treatment may penetrate the entiregraded cap layer 14 or is limited only to the surface of the graded caplayer 14. Example chemicals include adhesion promoters such as, forexample, silanes, siloxanes, and silylation agents. This treatment stepmay or may not be performed in the same tool as that used in forming thegraded cap layer 14.

Examples of such post deposition treatments are disclosed, for example,in U.S. Patent Application Publication No. 2008/0173984, the entirecontent which is incorporated herein by reference.

Referring to FIG. 2, a first patternable low-k material 18, whichcombines the function of a photoresist and low-k dielectric into onesingle material is provided directly on the surface of the graded caplayer 14. The first patternable low-k material 18 is provided (i.e.,formed) utilizing a deposition process including, for example,spin-on-coating, dip coating, brush coating, blade coating, and ink jetdispensing. After applying the first patternable low-k material 18, apost deposition baking step is typically, but not necessarily always,required to remove unwanted components, such as solvent. When performed,the baking step can be conducted at a temperature from 40° C. to 200°C., with a baking temperature from 60° C. to 140° C. being even morepreferred. The duration of the baking step varies from 10 seconds to 600seconds and is not critical herein.

The thickness of the first patternable low-k material 18 may varydepending on the requirement of the chip and the technique used to formthe same as well as the material make-up of the layer. Typically, thefirst patternable low-k material 18 has a thickness from 1 nm to 50000nm, with a thickness from 20 nm to 5000 nm being more typical.

As stated above, the first patternable low-k material 18 functions as aphotoresist and is converted into a low-k material during postpatterning processing, by heat, UV light, electron beam, ion beam,microwave, plasma cure, thermal cure or combinations thereof. Forinstance, the first patternable low-k material 18 may be a patternablecomposition comprising a functionalized polymer, copolymer, or a blendincluding at least two of any combination of polymers and/or copolymershaving one or more acid-sensitive imageable groups. This patternablecomposition can be converted into a low-k material after subsequentprocessing. It is noted that when the patternable low-k material 18 iscomprised of a polymer, the polymer includes at least one monomer (to bedescribed in greater detail below). When the patternable low-k material18 is comprised of a copolymer, the copolymer includes at least twomonomers (to be described in greater detail below). The blends ofpolymers and/or copolymers include at least two of any combination ofpolymers and/or copolymers described below.

In general terms, the patternable low-k material that can be employed aslayer 18 is a patternable composition comprising a polymer, a copolymer,or a blend including at least two of any combination of polymers and/orcopolymers, wherein the polymers include one monomer and the copolymersinclude at least two monomers and wherein the monomers of the polymersand the monomers of the copolymers are selected from a siloxane, silane,carbosilane, oxycarbosilane, silsesquioxane, alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.

More specifically, the first patternable low-k material 18 ispatternable composition comprising a photo/acid-sensitive polymer of onemonomer or a copolymer of at least two monomers selected from siloxane,silane, carbosilane, oxycarbosilane, organosilicates, silsesquioxanesand the like. The first patternable low-k material 18 may also bepatternable composition comprising a polymer of one monomer or acopolymer of at least two monomers selected from alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl (such as vinyl) substitutedsilsesquioxane, unsaturated alkyl substituted siloxane, unsaturatedalkyl substituted silane, an unsaturated alkyl substituted carbosilane,unsaturated alkyl substituted oxycarbosilane, carbosilane substitutedsilsesquioxane, carbosilane substituted siloxane, carbosilanesubstituted silane, carbosilane substituted carbosilane, carbosilanesubstituted oxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane. Additionally, the patternable low-k dielectric material18 may comprise a blend including at least two of any combination ofpolymers and/or copolymers, wherein the polymers include one monomer andthe copolymers include at least two monomers and wherein the monomers ofthe polymers and the monomers of the copolymers are selected from asiloxane, silane, carbosilane, oxycarbosilane, silsesquioxane,alkyltrialkoxysilane, tetra-alkoxysilane, unsaturated alkyl substitutedsilsesquioxane, unsaturated alkyl substituted siloxane, unsaturatedalkyl substituted silane, an unsaturated alkyl substituted carbosilane,unsaturated alkyl substituted oxycarbosilane, carbosilane substitutedsilsesquioxane, carbosilane substituted siloxane, carbosilanesubstituted silane, carbosilane substituted carbosilane, carbosilanesubstituted oxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.

Optionally the first patternable low-k material 18 may be patternablecomposition further comprising at least one microscopic pore generator(porogen). The pore generator may be or may not be photo/acid sensitive.By “photo/acid sensitive” it means that this porogen is sensitive tolight and/or acid such that the porogen itself is patternable orenhances the resolution and/or the pattern quality of the patternablelow-k material. This pore generator has these attributes: (1) iscompatible with the other components of the patternable low-kcomposition, i.e., without phase separation after coating and otherprocessing; (2) can be patterned with standard lithographic techniquesas part of the patternable low-k composition; and (3) can be removedduring the post patterning cure process to generate microscopic pores,thus lowering the dielectric constant of the cured patternable low-kmaterial. The pore size (diameter) should be less than 10 nm, preferablyless than 5 nm, and more preferably less than 2 nm.

Illustrative polymers for the patternable low-k material 18 include, butare not limited to, siloxane, silane, carbosilane, oxycarbosilane,silsesquioxane-type polymers including caged, linear, branched orcombinations thereof. In one embodiment, the first patternable low-kmaterial 18 is a patternable composition comprising a blend of thesephoto/acid-sensitive polymers. Examples of patternable low-k materialsuseable with the present disclosure are disclosed in U.S. Pat. Nos.7,041,748, 7,056,840, and 6,087,064, as well as U.S. Patent ApplicationPublication No. 2008/0286467, U.S. Patent Application Publication No.2009/0233226, and U.S. patent application Ser. No. 12/126,287, filed May23, 2008, all of which are incorporated herein by reference in theirentirety. The dielectric constant of the patternable low-k material 18after cure is generally no more than 4.3. The dielectric constant may begreater than 1 and up to 4.3, more preferably from 1 to 3.6, even morepreferably from 1 to 3.0, further more preferably from 1 to 2.5, withfrom 1 to 2.0 being most preferred.

The first patternable low-k material 18 is formed from a patternablecomposition that includes at least one of the above mentioned polymers,copolymers or blends, a photoacid generator, a base additive and asolvent typically used in a photoresists. When the first patternablelow-k material 18 is a negative-tone patternable low-k material, it maybe formed from a patternable composition optionally including anadditional cross-linker. This additional cross-linker can be a smallcompound (as compared with a polymer or copolymer) or a polymer, acopolymer, or a blend including at least two of any combination ofpolymers and/or copolymers, wherein the polymers include one monomer andthe copolymers include at least two monomers and wherein the monomers ofthe polymers and the monomers of the copolymers are selected from asiloxane, silane, carbosilane, oxycarbosilane, silsesquioxane,alkyltrialkoxysilane, tetra-alkoxysilane, unsaturated alkyl substitutedsilsesquioxane, unsaturated alkyl substituted siloxane, unsaturatedalkyl substituted silane, an unsaturated alkyl substituted carbosilane,unsaturated alkyl substituted oxycarbosilane, carbosilane substitutedsilsesquioxane, carbosilane substituted siloxane, carbosilanesubstituted silane, carbosilane substituted carbosilane, carbosilanesubstituted oxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.

When the first patternable low-k material 18 is a positive-tonepatternable low-k material, it is formed from a patternable compositionthat includes at least one of the above mentioned polymers, copolymersor blends, a photoacid generator, a base additive and a solventtypically used in a photoresists. The photoacid generators, baseadditives and solvents are well known to those skilled in the art and,as such, details regarding those components are not fully provided.

In a preferred embodiment, the first patternable low-k material 18 is achemically amplified positive-tone or negative-tone patternable low-kmaterial that comprises a silsesquioxane polymer or copolymer or a blendof at least two of any combination of polymers and/or copolymers. Thisphoto/acid sensitive silsesquioxane polymer or copolymer may undergo aphoto/acid catalyzed chemical transformation to form circuit patternsafter lithographic patterning. When the first patternable low-k material18 is a chemically amplified positive-tone patternable low-k material,it typically undergoes a de-protection reaction to render the exposedarea soluble in a developer; when the first patternable low-k material18 is a chemically amplified negative-tone patternable low-k material,it typically undergoes a cross-linking reaction (to itself or through anadditional cross-linker) to render it insoluble in a developer in theexposed regions during lithographic processing. Therefore, integratedcircuit patterns can be generated during standard semiconductorlithography process. Furthermore, these integrated circuit patternsmaintain their pattern integrity during the post patterning cure processto convert the patternable low-k material from a resist into a low-kmaterial. Examples of such photo/acid sensitive silsesquioxane polymersor copolymers include poly(methylsilsesquioxane) (PMS),poly(p-hydroxybenzylsilsesquioxane) (PHBS),poly(p-hydroxyphenylethylsilsesquioxane) (PHPES),poly(p-hydroxyphenylethylsilsesquioxane-co-p-hydroxy-alpha-methylbenzylsilsesquioxane) (PHPE/HMBS),poly(p-hydroxyphenylethylsilsesquioxane-co-methoxybenzylsilsesquioxane)(PHPE/MBS),poly(p-hydroxyphenylethylsilsesquioxane-co-t-butylsilsesquioxane)(PHPE/BS),poly(p-hydroxyphenylethylsilsesquioxane-co-cyclohexylsilsesquioxane)(PHPE/CHS),poly(p-hydroxyphenylethylsilsesquioxane-co-phenylsilsesquioxane)(PHPE/PS),poly(p-hydroxyphenylethylsilsesquioxane-co-bicycloheptylsilsesquioxane)(PHPE/BHS), polyp-hydroxy-alpha-methylbenzylsilsesquioxane) (PHMBS),polyp-hydroxy-alpha-methylbenzylsilsesquioxane-co-p-hydroxybenzylsilsesquioxane)(PHMB/HBS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-methoxybenzylsilsesquioxane)(PHMB/MBS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-t-butylsilsesquioxane)(PHMB/BS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-cyclohexylsilsesquioxane)(PHMB/CHS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-phenylsilsesquioxane)(PHMB/PS),poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-bicycloheptylsilsesquioxane)(PHMB/BHS),poly(p-hydroxybenzylsilsesquioxane-co-p-hydroxyphenylethylsilsesquioxane)(PHB/HPES), and poly(p-hydroxy-alpha-methylbenzylsilsesquioxane-co-p-alpha-methylbenzylsilsesquioxane)(PHMB/MBS). In one embodiment, the patternable low-k dielectric material18 is a copolymer of at least two monomers selected from analkyltrialkoxysilane and/or a tetra-alkoxysilane. Preferred copolymersare derived from at least two monomers selected frommethyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, orethyltriethoxysilane, as the alkyltrialkoxysilane monomer andtetra-methoxysilane or tetra-ethoxysilane, as the tetra-alkoxysilanemonomer.

In another embodiment, the first patternable low-k material 18 is apatternable composition comprising a polymer of one monomer or acopolymer of at least two monomers selected from alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl (such as vinyl) substitutedsilsesquioxane, unsaturated alkyl substituted siloxane, unsaturatedalkyl substituted silane, an unsaturated alkyl substituted carbosilane,unsaturated alkyl substituted oxycarbosilane, carbosilane substitutedsilsesquioxane, carbosilane substituted siloxane, carbosilanesubstituted silane, carbosilane substituted carbosilane, carbosilanesubstituted oxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane.

In one embodiment, the first patternable low-k material 18 is apatternable composition comprising a silsesquioxane polymer. It may belinear, branched, caged compound or combinations thereof having thefollowing general structural formula:

where, m and n represent the number of repeating units, R¹ represents agroup which may comprise one or more functional groups which may providepolymer solubility in an aqueous base and provide functional groups forcross-linking, and R² represents a group which may comprise a carbonfunctionality which may control polymer dissolution rate in an aqueousbase and/or an imaging function for positive-tone or negative-tonepatterning. Subscripts m and n may be integers in the range from 0 to50000, such as 1 to 5000 for example. R¹ may not be the same as R².

R¹ is not limited to any specific functional group, and may comprisefunctional groups which are substituted with —OH groups, —C(O)OH groups,—F, or combinations thereof, R¹ may comprise linear or branched alkyls,cycloalkyls, aromatics, arenes, or acrylics. For example, R¹ may be:

or the like.

R² is not necessarily limited to any specific functional group, and maycomprise hydrogen, or linear or branched alkyls, cylcoalkyls, aromatics,arenes, acrylates, or combinations thereof. For example R² may be:

or the like.

The R¹ and R² proportions and structures may be selected to provide amaterial suitable for photolithographic patterning processes.

In one embodiment, the first patternable low-k material 18 is anegative-tone patternable low-k dielectric material comprising a blendincluding at least two of any combination of polymers and/or copolymers,wherein the polymers include one monomer and the copolymers include atleast two monomers and wherein the monomers of the polymers and themonomers of the copolymers are selected from a siloxane, silane,carbosilane, oxycarbosilane, silsesquioxane, alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane. The polymers in the blend may be miscible with eachother. The first polymer or copolymer of the polymer blend has beendescribed above.

In some instances, the second polymer of the polymer blend of thisembodiment may comprise a polymer of one monomer or a copolymerincluding at least two monomers and wherein the monomers of the polymersand the monomers of the copolymers are selected from a siloxane, silane,carbosilane, oxycarbosilane, silsesquioxane, alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane. In one embodiment, the second polymer of the polymerblend may comprise a copolymer at least two monomers selected fromsiloxane, silane, silsesquioxane, carbosilane, or oxycarbosilanemoieties. In another embodiment of the present invention, the secondpolymer of the polymer blend may comprise a copolymer of at least twomonomers selected from an alkyltrialkoxysilane and/or atetra-alkoxysilane. The molar ratio of the alkyltrialkoxysilane monomerin the copolymer ranges from 0 to 100%. The weight average molecularweight of the copolymer range from 100-5,000,000 g/mol, preferably500-50,000 g/mol. Preferred second polymers of the polymer blend arecopolymers derived from at least two monomers selected frommethyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, orethyltriethoxysilane, as the alkyltrialkoxysilane monomer andtetra-methoxysilane or tetra-ethoxysilane, as the tetra-alkoxysilanemonomer. In one embodiment, the second polymer of the polymer blend is acopolymer of methylsilsesquioxane and tetra-alkoxysilane.

In another embodiment, the second polymer of the polymer blend is asilsesquioxane polymer comprising a polymer having the structuralformula:

wherein R³ may be a functional group comprising alkyls, cycloalkyls,aryl, or combinations thereof, and wherein x represents the number ofrepeating units and may be an integer in a range from 4 to 50000. Forexample, R³ may be:

or the like.

In one embodiment, the polysilsesquioxane may bepoly(methylsilsesquioxane), where R³ is a methyl group, and x is aninteger from 10 to 1,000. In other embodiments, x may be greater than1,000. The polysilsesquioxane may also comprise a copolymer withsiloxane, silane, carbosilane, oxycarbosilane, alkyltrialkoxysilane, ortetra-alkoxysilane. The polysilsesquioxane structure may be caged,linear, branched, or a combination thereof. The silsesquioxane polymersdescribed herein may comprise end groups comprising silanols,halosilanes, acetoxysilanes, silylamines, alkoxysilanes, or combinationsthereof, which may undergo condensation reactions in the presence of anacid (such as an acid generated by a photoacid generator under exposureto radiation), followed by thermal baking. Polymer molecules of thepolysilsesquioxane may undergo chemical crosslinking with the firstpolymer or copolymer of the polymer blend, the second polysilsesquioxanepolymer or copolymer in the polymer blend itself, or a combination ofthese.

In one embodiment, the polysilsesquioxane may be the silsesquioxanecopolymer LKD-2056 or LKD2064 (products of JSR Corporation) whichcontains silanol end groups. Such crosslinking may be not limited tosilanols, but may also include halosilanes, acetoxysilanes, silylamines,and alkoxysilanes. The silsesquioxane polymers described herein mayundergo chemical crosslinking, including photoacid-catalyzedcrosslinking, thermally induced crosslinking, or a combination of these,such as condensation reactions of silanol end groups, for example.

The second silsesquioxane polymers or copolymers in the polymer blendmay have a weight averaged molecular weight in the range from 200 to5,000,000 g/mol, such as from 1500 to 10,000 g/mol, for example.

In another embodiment, the first patternable low-k material 18 is anegative-tone patternable low-k material comprising acarbosilane-substituted silsesquioxane polymer that may be a linear,branched, caged compound or a combination thereof, having the followinggeneral structural formula:

where, a, b, and c represent the number of each of the repeating units,R⁴, R⁵, R⁶, R⁷, and R⁸ are carbon-containing groups, and R⁹ is an alkoxygroup. R⁶, R⁷ and R⁸ may each independently represent a hydrocarbongroup comprising 1 to 6 carbon atoms.

R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ may be non-identical groups. Subscripts a, b, andc represent the number of repeating units in the polymer chain.Subscripts q and r may be integers in a range from 0 to 3. Subscript smay be an integer in a range from 1 to 3. Subscripts a and c may beintegers greater than zero. For example a and c may each independentlybe in a range from 1 to 5,000. Subscript b may be an integer greaterthan or equal to zero. For example, b may be an integer in a range from0 to 5,000.

R⁴ may represent a group which comprises one or more functional groupswhich provide polymer solubility in an aqueous base and functionalgroups for a cross-linking reaction. Each instance of R⁴ is not limitedto any specific functional group, and may comprise a functional groupwhich is substituted with one or more —OH groups, —C(O)OH groups, —F, orcombinations thereof. R⁴ may comprise linear or branched alkyls,cycloalkyls, aromatics, arenes, or acrylics. Examples of R⁴ include:

or the like.

R⁵ may represent a group which comprises a carbon functionalitycomprising at least one carbon atom, where the carbon functionalitycontrols polymer dissolution of the polymer into an aqueous base. Thestructure (e.g., size, chain length, etc.) of R⁵ may affect thedissolution rate of the polymer into an aqueous base. Balancing of thedissolution-controlling group, R⁵, with the solubility and cross-linkingcontrolling group, R⁴, allows properties such as dissolution rate andaqueous base solubility to be appropriately adjusted. R⁵ is notnecessarily limited to any specific functional group, and may compriselinear or branched alkyls, cylcoalkyls, aromatics, arenes, acrylates, orcombinations thereof. Examples of R⁵ include:

or the like.

R⁶ is not limited to any specific alkoxy group. Examples of R⁶ includelinear or branched alkoxys, cycloalkoxy, and acetoxy groups.

The specific proportions and structures of R⁴, R⁵, and R⁶ may beselected to provide a material suitable for photolithographic patterningprocesses.

In another embodiment, the first patternable low-k material 18 is anegative-tone patternable low-k material comprising a polymer blend of afirst polymer or copolymer and a second polymer or copolymer wherein thefirst polymer is the carbosilane-substituted silsesquioxane polymerdescribed above and the second polymer is polymer of one monomer or acopolymer of at least two monomers selected from siloxane, silane,silsesquioxane, carbosilane, or oxycarbosilane moieties. In oneembodiment of the present invention, the second polymer of the polymerblend may comprise a copolymer of at least two monomers selected from analkyltrialkoxysilane and/or a tetra-alkoxysilane. The molar ratio of thealkyltrialkoxysilane monomer in the copolymer ranges from 0 to 100%. Theweight average molecular weight of the copolymer range from100-5,000,000 g/mol, preferably 500-50,000 g/mol. Preferred secondpolymers of the polymer blend are copolymers derived from at least twomonomers selected from methyltrimethoxysilane, methyltriethoxysilane,ethyltrimethoxysilane, or ethyltriethoxysilane, as thealkyltrialkoxysilane monomer and tetra-methoxysilane ortetra-ethoxysilane, as the tetra-alkoxysilane monomer. In oneembodiment, the second polymer of the polymer blend is a copolymer ofmethylsilsesquioxane and tetra-alkoxysilane.

In another embodiment, the negative-tone carbosilane-substitutedsilsesquioxane patternable low-k composition may be a patternablecomposition comprising a polymer blend of a first polymer and a secondpolymer wherein the first polymer is the carbosilane-substitutedsilsesquioxane polymer described above and the second polymer of thepolymer blend is a silsesquioxane polymer comprising a polymer havingthe structural formula:

wherein R³ may be a functional group comprising alkyls, cycloalkyls,aryl, or combinations thereof, and wherein x represents the number ofrepeating units and may be an integer in a range from 4 to 50000. Forexample, R³ may be:

or the like.

In one embodiment, the polysilsesquioxane may bepoly(methylsilsesquioxane), where R³ is a methyl group, and x is aninteger from 10 to 1,000. In other embodiments, x may be greater than1,000. The polysilsesquioxane may also comprise a copolymer withsiloxane, silane, carbosilane, oxycarbosilane, alkyltrialkoxysilane, ortetra-alkoxysilane. The polysilsesquioxane structure may be caged,linear, branched, or a combination thereof. The silsesquioxane polymersor copolymers described herein may comprise end groups comprisingsilanols, halosilanes, acetoxysilanes, silylamines, alkoxysilanes, orcombinations thereof, which may undergo condensation reactions in thepresence of an acid (such as an acid generated by a photoacid generatorunder exposure to radiation), followed by thermal baking. Polymermolecules of the polysilsesquioxane may undergo chemical crosslinkingwith the first polymer or copolymer of the polymer blend, the secondpolysilsesquioxane polymer or copolymer in the polymer blend itself, ora combination of these. In one embodiment, the polysilsesquioxane may bethe silsesquioxane copolymer LKD-2056 or LKD2064 (products of JSRCorporation) which contains silanol end groups. Such crosslinking may benot limited to silanols, but may also include halosilanes,acetoxysilanes, silylamines, and alkoxysilanes. The silsesquioxanepolymers described herein may undergo chemical crosslinking, includingphotoacid-catalyzed crosslinking, thermally induced crosslinking, or acombination of these, such as condensation reactions of silanol endgroups, for example.

The silsesquioxane polymers representing the second polymer of thepolymer blend described for this embodiment may have a weight averagedmolecular weight in the range from 200 grams/mole (g/mol) to 500,000g/mol, such as from 1500 g/mol to 10,000 g/mol, for example.

In another embodiment, compositions containing a blend of at least twoof any combination of a silsesquioxane polymer and/or a silsesquioxanecopolymer are employed. The silsesquioxane polymer or copolymer in theblend may be selected from the silsesquioxane polymers or copolymersdescribed above or may be selected from other silsesquioxane polymers orcopolymers such as, for example, poly(methyl-silsesquioxane) (PMS),poly(p-hydroxybenzylsilsesquioxane) (PHBS),poly(p-hydroxybenzylsilsesquioxane-co-methoxybenzylsilsesquioxane)(PHB/MBS),polyp-hydroxy-alpha-methylbenzylsilsesquioxane-co-p-alpha-methylbenzylsilsesquioxane)(PHMB/MBS), poly(p-hydroxybenzylsilsesquioxane-co-t-butylsilsesquioxane)(PHB/BS),poly(p-hydroxybenzylsilsesquioxane-co-cyclohexylsilsesquioxane)(PHB/CHS), poly(p-hydrooxybenzylsilsesquioxane-co-phenylsilsesquioxane)(PHB/PS),poly(p-hydroxybenzylsilsesquioxane-co-bicycloheptylsilsesquioxane)(PHB/BHS), and caged silsesquioxanes such asoctakis(glyeidyloxypropyl)dimethylsilyloxy)silsesquioxane,octakis[cyclohexenyl epoxide) dimethylsilyloxy]silsesquioxane,octakis[4-(hydroxyphenylethyl)dimethylsilyloxy]silsesquioxane, andoctakis[{2-(1′,1′-bis(trifluoromethyl)-1′-hydroxyethyl)norbornyl}dimethylsilyloxy]silsesquioxane.If desired, a combination of different Si-containing polymers may beused in the blend with the non-Si-containing polymers, such as a poregenerator.

In yet another embodiment, the first patternable low-k material 18 is apatternable composition comprising a copolymer of at least two monomersselected from an alkyltrialkoxysilane and/or a tetra-alkoxysilane.Preferred copolymers are derived from at least two monomers selectedfrom methyltrimethoxysilane, methyltriethoxysilane,ethyltrimethoxysilane, or ethyltriethoxysilane, as thealkyltrialkoxysilane monomer and tetra-methoxysilane ortetra-ethoxysilane, as the tetra-alkoxysilane monomer.

In a preferred embodiment for negative-tone patternable low-k materials,two miscible, or compatible, silsesquioxanes are employed. The firstsilsesquioxane polymer or copolymer is a linear, branched, cagedcompound or combination thereof having the following structural formula:

wherein each occurrence of R¹⁰ is one or more acidic functional groupsfor base solubility and provides functional groups for cross-linking;each occurrence of R¹¹ is a carbon functionality for controlling polymerdissolution rate in an aqueous base; R¹⁰ is not equal to R¹¹; j and krepresent the number of repeating units; j is an integer; and k is zeroor an integer greater than zero.

R¹⁰ is not limited to any specific functional group, and is preferablyselected from among linear or branched alkyls which are substituted withOH, C(O)OH, and/or F; cycloalkyls which are substituted with OH, C(O)OH,and/or F; aromatics which are substituted with OH, C(O)OH, and/or F;arenes that are substituted with OH, C(O)OH, and/or F; and acrylicswhich are substituted with OH, C(O)OH, and/or F. Examples of preferredR¹⁰ include:

R¹¹ is not limited to any specific carbon functional group, and ispreferably selected from among linear or branched alkyls, cylcoalkyls,aromatics, arenes, and acrylates.

The silsesquioxane polymers or copolymers of this embodiment have aweight averaged molecular weight of 400 to 500,000, and preferably from1500 to 10,000. The R¹⁰ and R¹¹ proportions and structures are selectedto provide a material suitable for photolithographic processes.

A second polymer component of the blend material includes but is notlimited to a family of organosilicates known as silsesquioxanes havingthe structural formula:

wherein R³ may be a functional group comprising alkyls, cycloalkyls,aryl, or combinations thereof, and wherein x represents the number ofrepeating units and may be an integer in a range from 4 to 50000. Forexample, R³ may be:

or the like.

In one embodiment, the polysilsesquioxane may bepoly(methylsilsesquioxane), where R³ is a methyl group, and x is aninteger from 10 to 1,000. In other embodiments, x may be greater than1,000. The polysilsesquioxane may also comprise a copolymer withsiloxane, silane, carbosilane, oxycarbosilane, alkyltrialkoxysilane, ortetra-alkoxysilane. The polysilsesquioxane structure may be caged,linear, branched, or a combination thereof. The silsesquioxane polymersor copolymers described herein may comprise end groups comprisingsilanols, halosilanes, acetoxysilanes, silylamines, alkoxysilanes, orcombinations thereof, which may undergo condensation reactions in thepresence of an acid (such as an acid generated by a photoacid generatorunder exposure to radiation), followed by thermal baking. Polymermolecules of the polysilsesquioxane may undergo chemical crosslinkingwith the first polymer or copolymer of the polymer blend, the secondpolysilsesquioxane polymer or copolymer in the polymer blend itself; ora combination of these. In one embodiment, the polysilsesquioxane may bethe silsesquioxane copolymer LKD-2056 or LKD2064 (products of JSRCorporation) which contains silanol end groups. Such crosslinking may benot limited to silanols, but may also include halosilanes,acetoxysilanes, silylamines, and alkoxysilanes. The silsesquioxanepolymers described herein may undergo chemical crosslinking, includingphotoacid-catalyzed crosslinking, thermally induced crosslinking, or acombination of these, such as condensation reactions of silanol endgroups, for example.

A third component of a negative-tone patternable low-k composition is aphotosensitive acid generator (PAG). Examples of preferred PAGs include:-(trifluoro-methylsulfonyloxy)-bicyclo[2.2.1]hept-5-ene-2,3-dicarboximide(MDT), onium salts, aromatic diazonium salts, sulfonium salts,diaryliodonium salts, and sulfonic acid esters of N-hydroxyamides or-imides, as disclosed in U.S. Pat. No. 4,371,605. The content of the'605 patent is incorporated herein by reference. A weaker acid generatedfrom a PAG such as N-hydroxy-naphthalimide (DDSN) may be used.Combinations of PAGs may be used.

The composition of the silsesquioxane polymers or copolymers in theblend formulation is 1 to 99% of the total polymer composition. In apreferred embodiment, the composition of the acid sensitive polymer is20 to 80% of the total polymer composition, and even more preferred, 30to 60%.

Condensation in the presence of an acid generated by a photoacidgenerator under exposure to radiation is not limited to silanols, butmay also include halosilanes, acetoxysilanes, silylamines, andalkoxysilanes. Organic crosslinking agents, such asmethylphenyltetramethoxymethyl glycouril (methylphenyl powderlink), mayalso be included in the formulation. Although photoacid generators arepreferred for crosslinking, photobase generators can also be used forcrosslinking silanol polymers or copolymers.

The first patternable low-k material 18 also typically includes acasting solvent to dissolve the other components. Examples of suitablecasting solvent include but are not limited to ethoxyethylpropionate(EEP), a combination of EEP and γ-butyrolactone, propylene-glycolmonomethylether alcohol and acetate, propyleneglycol monopropyl alcoholand acetate, and ethyl lactate. Combinations of these solvents may alsobe used.

In optimizing the photolithography process, an organic base may be addedto the formulation. The base employed in the present invention may beany suitable base known in the resist art. Examples of bases includetetraalkylammonium hydroxides, cetyltrimethylammonium hydroxide, and1,8-diaminonaphthalene. The compositions are not limited to any specificselection of base.

In yet another embodiment, the first patternable low-k material 18 is achemically amplified positive-tone patternable low-k material comprisinga silicon-containing polymer. The silicon-containing polymer employedmay be a homopolymer or a copolymer. Suitable types of suchsilicon-containing polymers include a polymer, a copolymer, a blendincluding at least two of any combination of polymers and/or copolymers,wherein said polymers include one monomer and said copolymers include atleast two monomers and wherein said monomers of said polymers and saidmonomers of said copolymers are selected from a siloxane, silane,carbosilane, oxycarbosilane, silsesquioxane, alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane. Highly preferred silicon-backbone polymers are selectedfrom the group consisting of poly(hydroxyphenyl alkyl)silsesquioxanesand poly (hydroxyphenyl alkyl) siloxanes, wherein the alkyl is a C₁₋₃₀moiety. These preferred silicon-containing polymers are preferably fullyor partially protected with acid-sensitive protecting groups.

In one embodiment, the first patternable low-k material 18 is achemically amplified positive-tone patternable low-k material comprisinga polymer of one monomer or a copolymer of at least two monomers whereina silicon-containing substituent is chemically bonded to the monomer ofthe polymers or copolymers. The silicon-containing substituent may ormay not be acid sensitive. Typically, however the substituent is acidsensitive when containing a C₂ alkyl moiety. Preferably, thesilicon-containing substituent is attached to a monomer selected fromthe group consisting of hydroxystyrene, an acrylate, a methacrylate, anacrylamide, a methacrylamide, itaconate, an itaconic half ester or acycloolefin. Preferred silicon-containing substituents include:siloxane, silane and cubic silsesquioxanes. The silicon-containingpolymer may further include silicon-free monomers such as those selectedfrom the group consisting of styrene, hydroxystyrene, acrylic acid,methacrylic acid, itaconic acid and an anhydride such as maleicanhydride and itaconic anhydride.

Preferred monomers containing silicon-containing substituents aretrimethylsilyl alkyl acrylate, trimethylsilyl alkyl methacrylate,trimethylsilyl alkyl itaconate, tris(trimethylsilyl)silyl alkyl acrylatetris(trimethylsilyl)silyl alkyl methacrylate, tris(trimethylsilyl)silylalkyl itaconate, tris(trimethylsilyloxy)silyl alkyl acrylate,tris(trimethylsilyloxy)silyl alkyl methacrylate,tris(trimethylsilyloxy)silyl alkyl itaconate, alkylsilyl styrene,trimethylsilylmethyl(dimethoxy)silyloxy alkyl acrylate,trimethylsilylmethyl(dimethoxy)silyloxy alkyl methacrylate,trimethylsilylmethyl(dimethoxy)silyloxy alkyl itaconate, trimethylsilylalkyl norbornene-5-carboxylate alkyl, tris(trimethylsilyl)silyl alkylnorbornene-5-carboxylate and tris(trimethylsilyloxy)silyl alkylnorbornene-5-carboxylate, wherein alkyl is a C₁₋₅ moiety.

Highly preferred species of these monomers are3-(3,5,7,9,11,13,15-heptacyclopentylpentacyclo[9.5.1.13,9.15,15.17,13]-octasiloxan-1-yl)propylmethacrylate,1,3,5,7,9,11,13-heptacyclopentyl-15-vinylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane,methacrylamidotrimethylsilane,O-(methacryloxyethyl)-N-(triethoxysilylpropyl)urethane,methacryloxyethoxytrimethylsilane,N-(3-methacryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane,(methacryloxymethyl)bis(trimethylsiloxy)methylsilane,(m,p-vinylbenzyloxy)trimethylsilane,methacryloxypropyltris(trimethylsiloxy)silane,methacryloxytrimethylsilane,3-methacryloxypropylbis(trimethylsiloxy)methylsilane,3-methacryloxypropyldimethylchlorosilane,methacryloxypropyldimethylethoxysilane,methacryloxypropyldimethylmethoxysilane,methacryloxypropylheptacyclopentyl-T8-silsesquioxane,methacryloxypropylmethyldichlorosilane,methacryloxypropylmethyldiethoxysilane,methacryloxypropylmethyldimethoxysilane,(methacryloxymethyl)dimethylethoxysilane,(methacryloxymethyl)phenyldimethylsilane(phenyldimethylsilyl)methylmethacrylate,methacryloxymethyltriethoxysilane, methacryloxymethyltrimethoxysilane,methacryloxymethyltris(trimethylsiloxy)silane,O-methacryloxy(polyethyleneoxy)trimethylsilane,methacryloxypropylpentamethyldisiloxane, methacryloxypropylsilatrane,methacryloxypropylsiloxane macromer, methacryloxypropyl terminatedpolydimethylsiloxane, methacryloxypropyltrichlorosilane,methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane,methacryloxypropyltris(methoxyethoxy)silane,p-(t-butyldimethylsiloxy)styrene, butenyltriethoxysilane,3-butenyltrimethylsilane, (3-acryloxypropyl)trimethoxysilane,(3-acryloxypropyl)tris(trimethylsiloxy)silane,O-(trimethylsilyl)acrylate, 2-trimethylsiloxyethlacrylate,N-(3-acryloxy-2-hydroxypropyl)-3-aminopropyltriethoxysilane,(3-acryloxypropyl)dimethylmethoxysilane,(3-acryloxypropyl)methylbis(trimethylsiloxy)silane,(3-acryloxypropyl)methyldichlorosilane, and(3-acryloxypropyl)methyldimethoxysilane,(3-acryloxypropyl)trichlorosilane.

When the first patternable low-k material 18 is a positive-tonepatternable low-k dielectric material comprising copolymers, the extentof protection and the amount of co-monomer present are such that thepatternable low-k material resist composition will provide goodlithography performance, i.e., high resolution and good process window.It should also maintain pattern integrity after post cure processingpatterning. Examples of protecting groups which can be employed arecyclic and branched (secondary and tertiary) aliphatic carbonyls, estersor ethers containing from 3 to 30 carbon atoms, acetals, ketals andaliphatic silylethers.

Examples of cyclic or branched aliphatic carbonyls that may be employedin the present invention include, but are not limited to: phenoliccarbonates; t-alkoxycarbonyloxys such as t-butoxylcarbonyloxy andisopropyloxycarbonyloxy. A highly preferred carbonate ist-butoxylcarbonyloxy.

Some examples of cyclic and branched ethers that may be employed in thepresent invention include, but are not limited to benzyl ether andt-alkyl ethers such t-butyl ether. Of the aforesaid ethers, it is highlypreferred to use t-butyl ether.

Examples of cyclic and branched esters that can be employed arecarboxylic esters having a cyclic or branched aliphatic substituent suchas t-butyl ester, isobornyl ester, 2-methyl-2-admantyl ester, benzylester, 3-oxocyclohexanyl ester, dimethylpropylmethyl ester, mevaloniclactonyl ester, 3-hydroxy-g-butyrolactonyl ester,3-methyl-g-butylrolactonyl ester, bis(trimethylsilyl)isopropyl ester,trimethylsilylethyl ester, tris(trimethylsilyl)silylethyl ester andcumyl ester.

Some examples of acetals and ketals that can be employed include, butare not limited to phenolic acetals and ketals as well astetrahydrofuranyl, tetrahydropyranyl, 2-ethoxyethyl,methoxycyclohexanyl, methoxycyclopentanyl, cyclohexanyloxyethyl,ethoxycyclopentanyl, ethoxycyclohexanyl, methoxycycloheptanyl andethoxycycloheptanyl. Of these, it is preferred that amethoxycyclohexanyl ketal be employed.

Illustrative examples of silylethers that can be employed include, butare not limited to: trimethylsilylether, dimethylethylsilylether anddimethylpropylsilylether. Of these silylethers, it is preferred thattrimethylsilylether be employed.

In one embodiment, the first patternable low-k material 18 is apositive-tone patternable low-k dielectric material comprising a blendincluding at least two of any combination of polymers and/or copolymers,wherein the polymers include one monomer and the copolymers include atleast two monomers and wherein the monomers of the polymers and themonomers of the copolymers are selected from a siloxane, silane,carbosilane, oxycarbosilane, silsesquioxane, alkyltrialkoxysilane,tetra-alkoxysilane, unsaturated alkyl substituted silsesquioxane,unsaturated alkyl substituted siloxane, unsaturated alkyl substitutedsilane, an unsaturated alkyl substituted carbosilane, unsaturated alkylsubstituted oxycarbosilane, carbosilane substituted silsesquioxane,carbosilane substituted siloxane, carbosilane substituted silane,carbosilane substituted carbosilane, carbosilane substitutedoxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane. The polymers in the blend may be miscible with eachother. The first polymer or copolymer of the polymer blend has beendescribed above.

In one embodiment, the first patternable low-k material 18 is apositive-tone patternable low-k material comprising a polymer blend ofat least two silsesquioxane polymers or copolymers. The polymers orcopolymers in the blend may be miscible with each other. The firstsilsesquioxane polymer or copolymer may be linear, branched, cagedcompound or combinations thereof having the following general structuralformula:

where, d, e and f represent the number of each of the repeating units,R¹² represents a carbon functionality (the carbon functionalitycomprising at least one carbon atom) having an acid-labile protectinggroup, R¹³ represents a group which may comprise one or more functionalgroups which provide polymer solubility in aqueous base, and R¹⁴represents a group which may comprise a carbon functionality comprisingat least one carbon atom, where the carbon functionality controlspolymer dissolution rate of the polymer blend into aqueous base. R¹²,R¹³, and R¹⁴ may be non-identical groups. Subscripts d, e, and frepresent the number of repeating units. Subscripts d and f may beintegers greater than zero. For example d and f may each independentlybe in a range from 1 to 5,000. Subscript e may be an integer greaterthan or equal to zero. For example, e may be an integer in a range from0 to 5,000.

R¹² is not limited to any specific carbon functional group, and may beselected from among conventional acid sensitive protecting groups, suchas carbonates, tertiary esters, acetals, ketals, the like, andcombinations thereof. For example, the acid sensitive protecting groupmay comprise a tert-butylacetate group, where R¹² may be:

R¹³ is not limited to any specific functional group, and may comprisefunctional groups which are substituted with —OH groups, —C(O)OH groups,—F, or combinations thereof. R¹³ may comprise linear or branched alkyls,cycloalkyls, aromatics, arenes, or acrylics. For example, R¹³ may be:

or the like.

R¹⁴ is not necessarily limited to any specific functional group, and maycomprise linear or branched alkyls, cylcoalkyls, aromatics, arenes,acrylates, or combinations thereof. For example R¹⁴ may be:

or the like.

The specific proportions and structures of R¹², R¹³, and R¹⁴ may beselected to provide a material suitable for photolithographic patterningprocesses.

In one embodiment, the second polymer of the polymer blend of thisembodiment of positive-tone patternable low-k material may comprise apolymer of one monomer or a copolymer including at least two monomersand wherein the monomers of the copolymers are selected from a siloxane,silane, carbosilane, oxycarbosilane, silsesquioxane,alkyltrialkoxysilane, tetra-alkoxysilane, unsaturated alkyl substitutedsilsesquioxane, unsaturated alkyl substituted siloxane, unsaturatedalkyl substituted silane, an unsaturated alkyl substituted carbosilane,unsaturated alkyl substituted oxycarbosilane, carbosilane substitutedsilsesquioxane, carbosilane substituted siloxane, carbosilanesubstituted silane, carbosilane substituted carbosilane, carbosilanesubstituted oxycarbosilane, oxycarbosilane substituted silsesquioxane,oxycarbosilane substituted siloxane, oxycarbosilane substituted silane,oxycarbosilane substituted carbosilane, and oxycarbosilane substitutedoxycarbosilane. In one embodiment, the second polymer of the polymerblend may comprise a copolymer of at least two monomers selected fromsiloxane, silane, silsesquioxane, carbosilane, or oxycarbosilanemoieties. In one embodiment of the present invention, the second polymerof the polymer blend may comprise a copolymer of at least two monomersselected from an alkyltrialkoxysilane and/or a tetra-alkoxysilane. Themolar ratio of the alkyltrialkoxysilane monomer in the copolymer rangesfrom 0 to 100%. The weight average molecular weight of the copolymerrange from 100-5,000,000 g/mol, preferably 500-50,000 g/mol. Preferredcopolymers are derived from at least two monomers selected frommethyltrimethoxysilane, methylmethoxysilane, ethyltrimethoxysilane, orethyltriethoxysilane, as the alkyltrialkoxysilane monomer andtetra-methoxysilane or tetra-ethoxysilane, as the tetra-alkoxysilanemonomer.

In another embodiment, the second polymer in the polymer blend for thepositive-tone patternable low-k material is a polymer having thestructural formula:

where R³ may be a carbon functional group having at least one carbonatom and wherein the subscript x represents the number of repeatingunits and may be an integer greater than zero. The subscript q may be ina range from 4 to 50,000, such as from 10 to 1,000 for example. R³ maycomprise, for example, alkyls, cycloalkyls, aryl, or combinationsthereof. Examples of R³ include:

or the like.

In one embodiment, the second silsesquioxane polymer may bepoly(methylsilsesquioxane) or copolymer, where R³ is a methyl group, andx is an integer from 4 to 1,000. In another embodiment, x may be greaterthan 1,000. The second silsesquioxane polymer may also comprise acopolymer with siloxane, silane, carbosilane, oxycarbosilane,alkyltrialkoxysilane, or tetra-alkoxysilane. The second silsesquioxanepolymer or copolymer structure may be caged, linear, branched, orcombinations thereof. The silsesquioxane polymers of the presentinvention may comprise end groups comprising silanols, halosilanes,acetoxysilanes, silylamines, alkoxysilanes, and combinations thereof,which may undergo condensation reactions in the presence of an acidgenerated by a photoacid generator under exposure to radiation, followedby thermal baking. Polymer molecules of the second polymer may undergochemical crosslinking with molecules of the first polymer or copolymer,the second polymer or copolymer, or a combination of these. In oneembodiment of the present invention, the second silsesquioxane may bethe silsesquioxane polymer or copolymer LKD 2021, LKD-2056 or LKD 2064(products of JSR Corporation) which contain silanol end groups.

The silsesquioxane polymers or copolymers in the polymer blend may havea weight averaged molecular weight in the range from 400 to 500,000g/mol, such as from 1500 to 10,000 g/mol, for example.

Other components of a positive-tone patternable low-k material include aphoto acid generator, a casting solvent and a base additive. Thesecomponents and their compositions are well known to those skilled in theart and are similar to those in the negative-tone patternable low-kmaterials discussed previously.

The term “photo/acid-sensitive” is used throughout the application todenote imageable functional groups which undergo a chemical reaction inthe presence of an acid generated by a photoacid generator underexposure to radiation. The acid-sensitive imageable functional groupsemployed may include acid-sensitive positive-tone functional groups oracid-sensitive negative-tone functional groups. The negative-toneacid-sensitive functional groups are functional groups for effecting acrosslinking reaction which causes the exposed areas to be insoluble ina developer to form a negative-tone relief image after development. Thepositive-tone acid-sensitive functional groups are acid-sensitiveprotecting groups which cause the exposed region to be soluble in adeveloper to form positive-tone relief images after development. Assuch, the patternable low-k material can be patterned with the standardlithography tool set.

The aforementioned patternable low-k materials act as a photoresistduring patterning; they can be positive-tone or negative-tone, andsensitive to G-line, I-line, DUV (248 nm, 193 nm, 157 nm, 126 nm, andEUV (13.4 μm), an electron beam, or an ion beam. The patterning byexposure with light through a mask can be in a dry mode or an immersionmode wherein a liquid with a refractive index larger than that of air isinserted between the patternable low-k and the lens of the exposuretool. The patterning of the patternable low-k material may beaccomplished with a single exposure or more than one exposure to formthe desired pattern.

In one preferred embodiment, a positive-tone patternable low-k material18 is used for via patterning. Either a positive-tone or a negative-tonepatternable low-k material 18 is used for line patterning.

Referring to FIG. 3, the first patternable low-k material 18 ispattern-wise exposed to form latent images of a desired circuitry. Anoptional post-exposure baking may be required to effect thephotochemical reactions. When performed, the baking step is conducted ata temperature from 60° to 200° C., with a baking temperature from 80° to140° C. being even more preferred. The duration of the baking stepvaries and is not critical to the practice of the present invention.After exposure and post-exposure baking, the latent images are developedinto the relief images with an appropriate developer, usually an aqueousbase solution, such as 0.26N tetramethylammoniahydroxide (TMAH)solution.

The pattern wise exposing process can be accomplished in a variety ofways, including, for example, through a mask with a lithography stepperor a scanner with an exposure light source of G-line, I-line (365 nm),DUV (248 nm, 193 mm, 157 nm, 126 nm), Extreme UV (13.4 nm), or anelectron beam, an ion beam. The exposing process may be performed in adry mode or an immersion mode. The pattern-wise exposing process alsoincludes direct writing without the use of a mask with, for example,light, electron beam, ion beam, and scanning probe lithography. Otherpatterning techniques that can be used include contact printingtechniques such as nanoimprint lithography, embroising, micro contactprinting, replica molding, microtransfer molding, micromolding incapillaries and solvent-assisted micromolding, thermal assistedembroising, inject printing, and the like.

FIG. 3 specifically illustrates the structure that is formed afterforming first interconnect patterns 20 within the patternable low-kmaterial film 18. The first interconnect patterns 20 may include atleast one via opening (as shown and as preferred) or at least one lineopening (not shown and less preferred than forming a via opening at thisstage of the inventive method). As shown, the first interconnectpatterns expose a surface of the graded cap layer 14.

After forming the first interconnect patterns, the patternable low-kmaterial 18 is typically, but not necessarily always, cured to form acured low-k material 18′ (See, FIG. 3). The curing is optional when thefirst patternable low-k material is negative-tone, but it is requiredwhen the first patternable low-k material is a positive-tone material.Curing is performed by a thermal cure, an electron beam cure, anultra-violet (UV) cure, an ion beam cure, a plasma cure, a microwavecure or a combination thereof. The conditions for each of the curingprocesses are well known to those skilled in the art and any conditioncan be chosen as long as it coverts the patternable low-k material intoa low-k film and maintains pattern fidelity.

In another embodiment, the irradiation cure step is performed by acombination of a thermal cure and an ultra-violet (UV) cure wherein thewavelength of the ultra-violet (UV) light is from 50 to 300 nm and thelight source for the ultra-violet (UV) cure is a UV lamp, an excimer(exciplex) laser or a combination thereof.

The excimer laser may be generated from at least one of the excimersselected from the group consisting of Ar₂*, Kr₂*, F₂, Xe₂*, ArF, KrF,XeBr, XeCl, XeCl, XeF, CaF₂, KrCl, and Cl₂ wherein the wavelength of theexcimer laser is in the range from 50 to 300 nm. Additionally, the lightof the ultra-violet (UV) cure may be enhanced and/or diffused with alens or other optical diffusing device known to those skilled in theart.

In one embodiment, this post patterning cure is a combined UV/thermalcure. This combined UV/thermal cure is carried on a UV/thermal curemodule under vacuum or inert atmosphere, such as N₂, He, Ar. Typically,the UV/thermal cure temperature is from 100° C. to 500° C., with a curetemperature from 300° to 450° C. being more typical. The duration of theUV/thermal cure is from 0.5 min to 30 min with a duration from 1 to 10min being more typical. The UV cure module is designed to have a verylow oxygen content to avoid degradation of the resultant dielectricmaterials. This post-patterning cure, if performed, may be in differentor the same tool cluster as that of the patterning step.

After patterning and optionally curing the first patternable low-kmaterial 18, a second patternable low-k material 22 is formed providingthe structure shown in FIG. 4. The second patternable low-k material 22may comprise the same or different material as the first patternablelow-k material 18. In general terms, the nature, the composition, andmethod of formulation mentioned above for the first patternable low-kmaterial 18 are each applicable here for the second patternable low-kmaterial 22. The deposition processes and thickness mentioned above forthe first patternable low-k material 18 are also each applicable herefor the second patternable low-k material 22. Typically, and in theembodiment illustrated, the first patternable low-k material 18 or thesecond low-k material 22 is either a negative-tone or a positive-tonematerial.

Referring now to FIG. 5, the second patternable low-k material 22 ispatterned to include second interconnect patterns 24. The patterning ofthe second patternable low-k material 22 is performed utilizing the samebasic processing equipment, steps and conditions as those used forpatterning the first patternable low-k dielectric material 18. In theillustrated embodiment, the second interconnect pattern 24 is typicallya line (trench). The via pattern formed within the first patternablelow-k material and subsequently filled when the second patternable low-kmaterial is form is also recovered. The second interconnect pattern 24may also be a via, when the first interconnect pattern is a line.

After patterning the second patternable low-k material 22, the structureis cured providing the structure shown in FIG. 6. In FIG. 6, referencenumeral 22′ denotes the cured second low-k material. Like the firstcured low-k material 18′, the cured second low-k material 22′ has arelative dielectric constant usually less than 4.3. If not previouslycured, this curing step also cures the first patternable low-k material18 into a cured low-k material 18′. The cure methods, equipment andprocesses mentioned above for the first patternable low-k material 18are each applicable here for the second patternable low-k material 22.

Still referring to FIG. 6, an etching step is performed that etchesthrough the graded cap layer 14. The etching step to ‘open’ the gradedcap layer 14 includes any etching process such as, for example, reactiveion etching or gas cluster ion beam etching.

A diffusion barrier layer (liner) (not shown), which may comprise Ta,TaN, Ti, TiN, Ru, RuTaN, RuTa, W, WN or any other material that canserve as a barrier to prevent electrically conductive material fromdiffusing through, is typically formed into the first and secondinterconnect patterns by a deposition process such as, for example,atomic layer deposition (ALD), chemical vapor deposition (CVD), plasmaenhanced chemical vapor deposition (PECVD), physical vapor deposition(PVD), sputtering, chemical solution deposition, or plating. In someembodiments (not shown), the diffusion barrier liner may comprise acombination of layers. The thickness of the diffusion barrier liner mayvary depending on the exact means of the deposition process employed aswell as the material and number of layers employed. Typically, thediffusion barrier liner has a thickness from 4 to 40 nm, with athickness from 7 to 20 nm being more typical.

Following the formation of the diffusion barrier layer (liner), theremaining region of the first and second interconnect patterns is filledwith an electrically conductive material 26 forming a conductivefeature. The conductive material 26 used in forming the conductivefeature includes, for example, polySi, an electrically conductive metal,an alloy comprising at least one electrically conductive metal, anelectrically conductive metal silicide, an electrically conductivenanotube or nanowire, graphene or combinations thereof. Preferably, theconductive material 26 that is used in forming the conductive feature isa conductive metal such as Cu, W or Al, with Cu or a Cu alloy (such asAlCu) being highly preferred in the present invention. The conductivematerial 26 is filled into the remaining first and second interconnectpatterns utilizing a conventional deposition process including, but notlimited to CVD, PECVD, sputtering, chemical solution deposition orplating. A preferred filling method is electrochemical plating.

After deposition, a conventional planarization process such as, forexample, chemical mechanical polishing (CMP) can be used to provide astructure in which the diffusion barrier layer and the conductivematerial 26 each have an upper surface that is substantially coplanarwith the upper surface of the cured second low-k material 22′. Theresultant structure after filling the openings in the cured first andsecond low-k materials and planarization is shown, for example, in FIG.7.

After forming the at least one conductive material 26 and planarization,another graded cap 14′ can be formed on the surface of the cured secondlow-k material 22′. The structure including another graded cap layer 14′is shown in FIG. 7. This graded cap 14′ can be formed utilizing themethods described above and graded cap 14 can comprise the same ordifferent composition as graded cap 14. In addition, the graded cap 14′can be replaced by any conventional dielectric cap.

In some embodiments not illustrated, a block mask can be formed atop thegraded (or conventional) cap 14′ utilizing any conventional depositionprocess including, for example, CVD, PECVD and spin-on coating. Theblock mask can comprise a standard photoresist material includinginorganic, organic and hybrid resists. The block mask can furthercomprise at least one anti-reflective coating layer and/or at least onehardmask layer. The composition of the anti-reflective coating layer andthe hardmask layer can be organic, inorganic or organic/inorganic hybridmaterials as long as the combination of their composition and layerthickness satisfies the patterning and pattern transfer needs of asubsequent airgap. In this particular embodiment, the graded cap 14′ andblock mask are patterned providing an airgap pattern therein. Thepatterning step includes optical lithography, immersion lithography,EUV, soft lithography, contact printing, nano-printing, E-Beam, masklessdirect writing, scanning probe lithography, self-assemble lithographyand directed self-assemble lithography. Note that the feature size ofthe airgap pattern is less than the dielectric spacing within the low-kmaterials. The patterning step also includes etching such asreactive-ion etching. The airgap pattern can be transferred into atleast the second patterned and cured low-k material 22′ utilizing atimed etching process such as, for example, reactive ion etching. Aftertransferring the airgap pattern into the second patterned and curedlow-k dielectric material 22′, the airgap is formed with the secondpatterned and cured low-k dielectric material 22′ selectively removingpart of the second patterned and cured low-k dielectric material 22′.The remaining block mask is then removed from the structure utilizing aconventional removal method of sacrificial materials such as reactiveion etching, stopping atop the remaining graded cap 14′. In thisembodiment, the transferred airgap pattern is adjacent to, but notdirectly abutting the conductively filled regions formed into at leastpatterned and cured second patternable low-k material. The airgappattern may also be extended into the first patterned and curedpatternable low-k material 18′.

After transferring the airgap pattern into at least the patterned andcured second low-k material 22′, portions of the low-k material that aredirectly abutting the airgap opening are changed physically, chemicallyor both so as to have a different removal rate as compared to theremaining low-k dielectric material. This change in removal rate isachieved in the present application, by a chemical treatment, exposureto a reducing or an oxidizing plasma. One preferred embodiment of thismaterial transformation is by an isotropic reactive ion etching. Theisotropic ion etching gas chemistry is selected from at least one of O₂,CO, CO₂, N₂, H₂, NH₃, He, Ar, hydrocarbon and the like. This changedportion of the low-k dielectric directly abutting the airgap opening isthen removed utilizing an etching process such as, for example, anisotropic etch utilizing a dilute HF etchant. A supercritical fluidetching process may also be used in some embodiments of the invention.These two steps, e.g., changing the etch selectivity of portions of thepatterned and cured low-k dielectric material and etching, provides anairgap within the structure. The airgap may include air or a vacuum. Apump may be used to remove the air from the airgap to form a vacuum. Anairgap cap can be formed atop the remaining another cap layer 14′sealing the airgap in the structure. The airgap cap includes an ARCincluding a conventional inorganic ARC. FIG. 9 illustrates theinterconnect structure of FIG. 8 after aircap 38 formation. FIG. 9 alsoshows airgap cap 40 atop the structure.

In addition to the dual-damascene embodiment mentioned above, thepresent invention also contemplates a single-damascene embodiment. Thesingle-damascene structure includes the same basic processing steps asdescribed above for the dual-damascene process except that a secondpatternable low k dielectric is not introduced into the process.

The following examples illustrate some aspects of the present invention.

Example 1

As summarized in the table below, five films were deposited onto siliconsubstrates at 400° C., high frequency rf power was varied between300-460 Watts, and the pressure was varied between 3-8.7 torr. Trimethylsilane was selected as the carbon and silicon source, ammonia as thenitrogen source and He was used as a dilutant.

Layer TMS (sccm) NH₃ (sccm) He (sccm) pressure power 1 80 160 200 3 3002 160 160 240 8.7 460 3 160 100 300 8.7 460 4 160 50 350 8.7 460 5 160 0400 8.7 460

The effect of varying trimethyl silane, ammonia flows was studied byFTIR (not shown). As shown in the FTIR spectra decreasing ammonia in thefilm decreases SiN and increases SiC, CH and SiH content in the film.

Example 2

Using the individual conditions from layer 1-5 in example 1, a gradedlayer was deposited. Deposition time was varied for each layer tooptimize film thickness and properties.

While the present invention has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present invention. It is therefore intended that the presentinvention not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

1. An interconnect structure comprising: at least one patterned andcured low-k material located directly on a surface of a patterned gradedcap layer, wherein said at least one patterned and cured low-k materialand said patterned graded cap layer each have conductively filledregions embedded therein, wherein said patterned and cured low-kmaterial is a cured product of a patternable composition comprising afunctionalized polymer, copolymer, or a blend including at least two ofany combination of polymers and/or copolymers having one or morephoto/acid-sensitive imageable groups, and said graded cap layerincludes a lower region that functions as a barrier region and an upperregion that has the properties of a permanent antireflective coating,wherein said lower region and said upper region are separated by atleast one middle region.
 2. The interconnect structure of claim 1further comprising at least one airgap located within that at least onepatterned and cured low-k material adjacent, but not directly abuttingthe conductively filled regions.
 3. The interconnect structure of claim1 wherein said at least one middle region is derived from a combinationof an anti-reflective precursor and a dielectric cap precursor.
 4. Theinterconnect structure of claim 1 wherein said graded cap layer is acontinuous layer with a gradually varied composition along the verticaldirection.
 5. The interconnect structure of claim 1 wherein said lowerregion of the graded cap layer includes atoms of Si and C; atoms of Siand N; atoms of Si and O, atoms of Si, O and N; atoms of Si, C and O;atoms of Si, C, O and H; or atoms of Si, C, N and H.
 6. The interconnectstructure of claim 1 wherein said lower region of the graded cap layercomprises atoms of Ru, Co, W and P.
 7. The interconnect structure ofclaim 1 wherein said graded cap layer has a thickness range from 2 nm to200 nm.
 8. The interconnect structure of claim 1 wherein said upperregion comprises atoms of Si, C, O, N and H; atoms of Si and C; atoms ofSi, O and C; atoms of Si, C, O and H; and atoms of W, Co, Ru, Ta, Ti,and Ru.
 9. The interconnect structure of claim 1 wherein said upperregion includes atoms of M, C and H, wherein M is selected from at leastone atom of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La.
 10. Theinterconnect structure of claim 9 further comprising at least one atomof O, N, S or F.
 11. The interconnect structure of claim 1 wherein saidupper region comprises a vapor deposited M:C:H film wherein M isselected from at least one atoms of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hfand La.
 12. The interconnect structure of claim 11 further comprising X,wherein is at least one atom of O, N, S or F.
 13. The interconnectstructure of claim 1 wherein said upper region comprises a polymer thathas at least one monomer unit of the formula M-R^(A) wherein M is atleast one of the elements of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La,and R^(A) is a chromophore.
 14. The interconnect structure of claim 13wherein M of the at least one monomer unit is bonded to an organicligand selected from elements of C and H, a cross-linking component,another chromophore and mixtures thereof.
 15. The interconnect structureof claim 13 further comprising another monomer unit, said anothermonomer unit having the formula M′-R^(B), wherein M′ is at least one ofthe elements of Si, Ge, B, Sn, Fe, Ta, Ti, Ni, Hf and La, and R^(B) is across-linking component.
 16. The interconnect structure of claim 13wherein M and M′ is bonded to an organic ligand selected from elementsof C and H, a cross-linking component, another chromophore and mixturesthereof.
 17. An interconnect structure comprising: a lower patterned andcured low-k material located directly on a patterned graded cap layerand an abutting upper patterned and cured low-k material located on saidlower patterned and cured low-k material, said lower and upper patternedand cured low-k materials and said patterned cap layer each havingconductively filled regions, wherein said patterned and cured upper andlower low-k materials each are cured products of a same or differentpatternable composition comprising functionalized polymer, copolymer, ora blend including at least two of any combination of polymers and/orcopolymers having one or more photo/acid-sensitive imageable groups, andsaid graded cap layer includes a lower region that functions as abarrier region and an upper region that has properties of a permanentantireflective coating, wherein said lower region and said upper regionare separated by at least one middle region.
 18. The interconnectstructure of claim 17 wherein said at least one middle region is derivedfrom a combination of an anti-reflective precursor and a dielectric capprecursor.
 19. An airgap-containing interconnect structure comprising: alower patterned and cured low-k material located directly on a patternedgraded cap layer and an abutting upper patterned and cured low-kmaterial located on said lower patterned and cured low-k material, saidlower and upper patterned and cured low-k materials and said patternedcap layer each having conductively filled regions, wherein saidpatterned and cured upper and lower low-k materials each are curedproducts of a same or different patternable composition comprisingfunctionalized polymer, copolymer, or a blend including at least two ofany combination of polymers and/or copolymers having one or morephoto/acid-sensitive imageable groups, and said graded cap layerincludes a lower region that functions as a barrier region and an upperregion that has properties of a permanent antireflective coating,wherein said lower region and said upper region are separated by atleast one middle region.
 20. A method of fabricating an interconnectstructure comprising: providing a graded cap layer on a surface of asubstrate, said graded cap layer includes a lower region that functionsas a barrier region and an upper region that has properties of apermanent antireflective coating, wherein said lower region and saidupper region are separated by at least one middle region; providing atleast one patternable low-k material directly on a surface of the gradedcap layer, wherein said at least one patternable low-k material is apatternable composition comprising a functionalized polymer, copolymer,or a blend including at least two of any combination of polymers and/orcopolymers having one or more photo/acid-sensitive imageable groups;forming at least one interconnect pattern within said at least onepatternable low-k material and said graded cap layer, said at least oneinterconnect pattern within said at least one patternable low-k materialis formed without utilizing a separate photoresist material; curing saidat least one patterned patternable low-k material into cured dielectricmaterial having a dielectric constant of not more than 4.3; and fillingsaid at least one interconnect pattern with an electrically conductivematerial.
 21. The method of claim 20 further comprising; forming a stackcomprising another graded cap layer and a block mask atop said cureddielectric material; forming at least one airgap through said stack andinto cured dielectric material; and forming an airgap cap atop saidanother graded cap of said stack.
 22. The method of claim 21 whereinsaid forming at least one airgap through said stack and into said cureddielectric material includes a gap transfer process, followed byphysical or chemical change or both of portions of the cured dielectricmaterial directly adjacent to the airgap pattern transferred therein,and selective removal of the changed portions of the cured dielectricmaterial.
 23. The method of claim 20 wherein said patterned graded caplayer is formed by deposition, lithography and etching, said depositionincludes a gas phase deposition, a liquid phase deposition or acombination of gas phase and liquid depositions.
 24. A method offabricating a dual-damascene interconnect structure comprising:providing a graded cap layer on a surface of a substrate, said gradedcap layer includes a lower region that functions as a barrier region andan upper region that has properties of a permanent antireflectivecoating, wherein said lower region and said upper region are separatedby at least one middle region; providing a first patternable low-kmaterial directly on a surface of the graded cap layer, wherein firstpatternable low-k dielectric material is a patternable compositioncomprising a functionalized polymer, copolymer, or a blend including atleast two of any combination of polymers and/or copolymers having one ormore photo/acid-sensitive imageable groups; forming first interconnectpatterns within the first patternable low-k material without a separatephotoresist; providing a second patternable low-k material on top of thefirst patterned low-k material including said first interconnectpatterns, said second patternable low-k material has a same or differentcomposition as said first patternable low-k material; forming secondinterconnect patterns within said second patternable low-k materialwithout a separate photoresist; curing at least said second patternedpatternable low-k material; opening exposed portions of the graded caplayer; and filling said first and second interconnect patterns and saidopening within the graded cap layer with an electrically conductivematerial.
 25. The method of claim 24 further comprising: forming a stackcomprising another graded cap and a block mask located atop said curedsecond patternable low-k material; forming at least one airgap throughsaid stack and into at least said cured second patternable low-kmaterial; and forming an airgap cap atop said another graded cap of saidstack.